I think it's kind of non-linear. You have a user with ~18000 karma wagering against a user with ~6000 karma. Moving from 18000 to 17000 karma would have no impact on rms' HN experience or general ranking. Similarly, paul is not going to get any big bump in going from 6000 to 7000.
Now, if paul was a new user with 5 karma, the 1000 point bump would open up options on HN that he did not previously have. It would also boost his perceived ranking slightly from an unvetted newbie to someone with roughly first-tier status.
So, the value of 1000 karma isn't some baseline value multiplied by 1000. It varies by user based on the relative impact it has to that user.
To me it is the old Gentleman's bet of a dollar. More or less worthless outside of the fact that you must admit defeat, and surrender something. The thing surrendered doesn't matter or have any value beyond the symbolic.
Why should anyone care? If you base your value of someone's opinion on their karma then you aren't really thinking for yourself. Someone with 1000's of karma points (even hundreds) just means they've been around a while, spent quite a bit of time, and had enough posts that resonated on the front page. Dig through posts that get few comments and you'll find some gems (they've just been overlooked).
And, really, what is the value of karma? Comment first and be insightful or funny - likely to get points if it hits front page. Comment late and be insightful or funny - likely to get a couple of points if it stays front page. Comment on anything not on front page - likely to be overlooked and even if you are insightful you may not get any karma, even from the OP.
Karma is kinda silly and even talking about it is sillier.
The price of one karma point is upper-bounded by the cost of making it yourself. Since you could just create a sock puppet to upvote yourself (assuming newbies may vote -- haven't kept track of the catalog) in a minute, and the minute is worth $0 (because HN is a sweet waste of time), one karma point can't cost more than $0.
However, the price isn't linear. You can't boost yourself by a million that way because PG would notice. So million-point karma packages could actually have a nonzero monetary value.
Creating an account to upvote yourself is against the rules and HN has sock-puppet detection software that is not fully published in the open source release of news.arc. Reddit similarly has sock puppet detection software... all social news sites beyond a certain size need software like this or things like the home page being taken over by internet marketers happens.
Now, if paul was a new user with 5 karma, the 1000 point bump would open up options on HN that he did not previously have. It would also boost his perceived ranking slightly from an unvetted newbie to someone with roughly first-tier status.
So, the value of 1000 karma isn't some baseline value multiplied by 1000. It varies by user based on the relative impact it has to that user.