
Show HN: I made a site that calculates the market price of items on ebay - locksley
http://www.getmarketprice.com/
======
locksley
This was my weekend project. I made it after being frustrated at not knowing
what a fair price for an iphone 5 would be on eBay. I posted this a month ago
but wasn't ready for HN traffic. Learnt about load testing the hard way and
have optimized it since. So, here it is again.

Feel free delve into any questions.

~~~
slashdotdash
Neat site, thanks for sharing. Here's some constructive feedback for you.

* Filter results by eBay category.

* Outlier elimination such as excluding "broken" items (e.g. listings containing commonly used words such as "spares or repair", "cracked screen", "damaged").

* Country specific currency (e.g. for UK searches show the results in GBP, £).

* Predict a fair market value for a given search. Useful when trying to sell items second hand as an "arm's-length transaction".

~~~
jherrick
Good list. I would also suggested eliminating outlying items based on prices.
It seems like when there are dozens of items named XXX, there will be several
with "hard drive for XXX" or something.

I must believe there's any easy way to eliminate some "outliers" using
mathematics, but I can't recall the function(s) to do so.

~~~
SandB0x
> I must believe there's any easy way to eliminate some "outliers" using
> mathematics, but I can't recall the function(s) to do so.

The median is one good way, as you already have. You can also use the
interquartile mean: <http://en.wikipedia.org/wiki/Interquartile_mean>

~~~
locksley
At the moment I'm filtering out items 2 standard deviations out of the median.
It catches the ridiculous cases, i.e. when some fool tries to get away with
selling an iphone for $6000 (yes I've seen this before).

Perhaps I need to filter it within 1 or 1.5 stdevs. Will experiment with this.

However, sometimes you can easily see there are two clusters of results. Not
sure how to mathematically determine this. Any ideas?

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regularfry
The search term "win&win riser" breaks it. Looks like you're not url-escaping
the search term?

EDIT - also it looks like you're submitting it to ebay badly, the results for
"win&win" are same as for "win".

~~~
locksley
Ahh, thanks for the heads up. I'm using a URI Escape function on the search
terms and that might be breaking something. Looking into it now.

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tharshan09
This is a really nice little app. I mean I have only used ebay only a couple
of times but this is really nice, and its something I kinda wish I had at the
back of my mind when using ebay.

Can you give a little details on how it works? Is it scraped data? etc.

I know this is targeted at a person who wants to sell items on ebay, but I am
a buyer and I find this still quite useful. Not sure how up to date the data
is but the graphs are an amazing feature! Makes so much sense.

~~~
locksley
Thanks for the comments!

I actually originally intended this for the buyer! I wanted an iphone for
myself, so I scraped the 'completed listings' page on ebay, and converted it
to csv to build a histogram in excel.

The data is up to the minute. But I cache the queries in order the save
computational resources. Each cache expires within 15 minutes.

Initially the data was scraped, but then I moved to the API which improved
performance by 200 - 300%.

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h2s
Bug report: choosing US, UK or AUS from the country select dropdown causes the
form to submit as if you'd typed in the country code as your search term.

This is a really killer piece of kit though. I'm very impressed. It's
something I think many of us have idly imagined when struggling to determine a
good starting price for a new eBay auction.

~~~
locksley
Ah Crap, thanks for letting me know. I'll patch it up tomorrow, it's 12:30am
here in Melbourne!

------
booruguru
Very neat site. I think overtime, you should try to find more visually
pleasing ways of presenting the data, but for now it's not a deal breaker.

I have a suggestion: Perhaps you could build some kind of e-mail alert system
that lets me know when there's an e-bay "Buy Now" item available within a user
specified price range. You could also let me know if there an item I want is
still within a certain price range hours before the bid closes.

EDIT: Typos.

~~~
locksley
You don't like the charts?

I'm guess a stats nerd so I like to see that stuff haha.

I like your feature suggestion, just put it in my product backlog.

~~~
hobs
Do not remove the charts. I love the charts.

They are simple and obvious, the only feedback I would give is that I would
think (not being a huge ebay person) the current charts might actually be
changed up a bit. I would be more interested in seeing the clustering of
prices, or something like how long the listing has ran without a bid
(indicating more likely desperate takers and the like). If the current charts
do influence the price in some way that can be used that is advantageous to
the buyer, then I would rescind my comment.

Sent this site to a few friends who don't read HN, they are highly
appreciative.

------
GotAnyMegadeth
Suggestion: You should be able to exclude certain data items from the
calculation, then recalculate (check box for exclude next to the raw data item
or something). I just did a search for "fender aerodyne bass guitar" and the
lowest price that came up was $249.99, though that turned out to be only the
neck of a bass "2007 Fender Aerodyne JAZZ BASS NECK Tuners Bass Guitar Black
Headstock".

~~~
locksley
That's a good idea. I'm planning to build a pricing filter slider on the
results page because it seems most people have a rough idea how much an item
is worth.

Your problem was the reason why I filtered out results below $100. There's
just too much junk below that range like "Fender Bass HELLO KITTY STRAP".
Eventually I'll have to think of a way to algorithmically exclude those
results.

Thanks for the suggestion.

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nos4A2
Looks awesome! Some outlier elimination would be great (on a search for a
graphics card there was skew due to unrelated items)

~~~
locksley
Hey thanks! I'm just using a filter of 2 standard deviations within the median
at the moment. Any ideas on how to do it more effectively?

------
booruguru
Dude, put a contact link on your site so people can give feedback. Also, once
someone does a search, you should pass the search query into the search box so
they can make modifications without retyping the whole thing.

~~~
locksley
Yeah, that's on the product backlog! But I'm a full time law student doing
this as a side project in order to learn how to code.

NEED MOAR ENGINEERS

------
nekgrim
And you're on lifehacker : [http://lifehacker.com/5986983/market-price-
calculates-what-y...](http://lifehacker.com/5986983/market-price-calculates-
what-youll-get-for-an-item-on-ebay)

Congratulations!

~~~
locksley
This was crazy, thanks for letting me know!

My servers surprisingly seemed to handle it ok with one minor crash.

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xur17
Is there any way to search for a certain condition only? When I search for the
iPhone for example, it returns a huge range of prices that include ones that
were used and refurbished.

Otherwise, it looks like a great site!

~~~
locksley
Ebay's API might have a 'condition' property, I shall check.

In the meantime it's probably just as effective to put the condition as a
query, i.e "iPhone 5 used"

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nawitus
Nice site, but I would like a third graph which shows (e.g.) the average price
(for the day) in the y-axis and days in x-axis, so you can estimate how the
price has developed over the last few weeks.

~~~
locksley
Yeah this would be interesting and I can certainly do it for popular searches.

To do it for all items would require collection of lots of data in my own
database though. Will have a think about this.

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lilfeetpete
Great job, in addition to the comments already made I think it would be more
useful if it said what you would make from a sale after ebay and paypal take
their cut from the sale.

~~~
slashdotdash
Agreed, that's a great suggestion. It's always surprising just how much of a
cut the eBay & PayPal fees take away from the final sale price.

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xabi
Nice site! Could you please add more countries? Spain (ebay.es)?

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rokahnhn
Possible bug report: I searched for "thunderbolt LCD" and [recently ended
graph] doesn't seem to match up with prices in [recently ended table].

~~~
locksley
Hey you sure about that? Seems to be fine for me. But there are two obvious
clusters. Perhaps two different LCD models?

<http://www.getmarketprice.com/results/thunderbolt-LCD/>

------
jbrooksuk
Clever idea, it's always time consuming to explain to my father in law that
he'd be better off buying something new in the shop or online.

~~~
locksley
Thanks! Similarly, I've convinced my grandma to use this.

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makethetick
Looks great and could be a very handy tool but I would of expected prices to
show up in £ rather than $ when selecting UK.

~~~
locksley
Thanks for the pick up.

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ericcholis
Small bug, searching for "2012/13 Panini Elite Basketball Hobby Box" confuses
your URL pattern, only searching for "2012"

~~~
locksley
Ah balls. I'm on it.

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therobot24
seems to break when i put in a specific season, ex:

\- "dexter season 6" returns only listings where season 1-6 are sold setting
an average price at ~$140 \- "simpsons season 9" returns listings where
multiple seasons including season 9 are sold setting the an average price at
~$150

In each case the 'raw data' had more than one season in it

~~~
locksley
Hmmm, this is difficult to fix because it relies on Ebay's search engine. The
only solution I could think of is to add a 'price filter slider' on the
results page. This way, you could set the limits to how much you think Dexter
Season 6 should cost.

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EvaK_de
Ah, that comes very handy! Thanks.

Would it be possible to show the full link when hovering over a truncated link
("lin...")?

~~~
locksley
I guess this would be simple enough. From what I know, it'd just be adding a
title attribute with the full text in the anchor tag.

------
joshcrowder
This is great, very impressive. When searching for an item in the UK the price
still shows in dollars.

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xanmas
I tried to search for a speedmaster 3510.50 and it cut off everything after
the period. Regex issue?

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radiospiel
Just curious: this is not in line w/ebay's T&C, or is it? Quite impressive,
anyways.

~~~
fishpi
When I looked at doing the same thing a few years ago, I found it was
explicitly ruled out in the conditions attached to the eBay API. There may be
a way to get by under the radar, but I considered it a sufficiently sketchy
business model I abandoned the idea.

~~~
ahmadss
if you're not using ebay's api, then how are you gathering this data? or am i
reading this incorrectly and you are indeed using ebays api?

~~~
hobs
That is not the creator of this tool. The maker is quoted earlier in the
thread talking about the API usage increasing the speed of the process by
200-300%, so he is definitely using the API.

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frantissek
Hey, I like it so. If want to design-up that site, let me know. Fkrivda.com

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momop
Nicely done and Good luck!

------
styluss
What's your stack?

~~~
locksley
Rails (without ActiveRecord/Database) Heroku Unicorn Server

