How about a $1 bill priced at $2 w/free shipping? From every angle, it would be an interesting experiment. From the consumer's standpoint, it challenges the notion of free shipping. From a seller's standpoint, it challenges the notion of easy money (would you really want to stuff a thousand envelopes if the item sold well?). From the middleman's standpoint, it might help to identify bots (or possibly even money laundering).
A bunch of engineers at idealab did this back during the bubble. The idea was the saturate Pasadena, CA with $2 bills, particularly as retailers, lacking anywhere to put $2 bills in registers, tended to quickly re-release them.
We tried buying them a thousand at a time from banks. One time a manager came out to talk to us about it and asked what we wanted them for. We explained and his response was, "So we're going to get them all back."
They do try to discourage the airmiles-purchasing behaviour:
"The immediate bank deposit of $1 coins ordered through this Program does not result in their introduction into circulation and, therefore, does not comply with the intended purpose of the program."
"There is a 4-box $1 coin limit for every 10-day period on any and all $1 coin orders. Beyond that your credit card will not be authorized. If you need quantities greater than this, please send an e-mail before placing your order to firstname.lastname@example.org explaining why your order should be exempted from the limit."
To do this right, you have to be able to change the terms of the auction. Allow bidding for the $1 to start at a penny so it seems like a good deal. Then allow that the highest bidder gets the dollar, but doesn't have to pay... and the second-highest bidder must pay his bid amount, but receives nothing.
You should see dollar bills purchased for hundreds of dollars at least.
"The only way to win is not to play the game." </wargames>
Yeah, the busy part of me has too many other things to do as well, but if you need someone to feed you dozens of other ways to use game theory to abuse people, it'd be worth it just for all the headdesk in seeing them implemented.
selling $1 bills would likely be difficult using the bot in the article because the site (trademe.co.nz) is only in New Zealand where the smallest bill is the $5 one. Although there are probably other equally effective sales you could run using $1 and $2 coins.
That would be a pretty bad idea since checks include all the information someone needs to make hard to reverse withdrawals from your account. Knuth used to send checks but no longer does. See http://sunburn.stanford.edu/~knuth/news08.html.