The following suggests that a user with a reputation score of 100,000 has done about £20,000 ($27,000) of work for the company.
Pending the investigation of the applicability of Bathsheba's excellent suggested model, I took a sample of 25 users of Stack Overflow and for each of them I looked at their reputation score and the number of "people reached". The sample comprised the authors of the five answers posted here prior to this one, along with the lowest-score users on each of pages 1-5, 51-55, 101-105 and 201-205 of the listing of SO users by rep.
A linear regression with the intercept set at 0 rep = 0 views gives a goodness of fit R2 = 0.833 and a figure of 77 views per rep point. So if 1000 views are worth $1 to an advertiser, that's $77x per 1000 rep where x is the average number of pages a visitor views here.
R2 jumps to 0.89 if two very high views-to-rep users are removed.
An estimate based on what's been written so far would be maybe $80-$400 (£60-£300) per 1000 rep, or $16-$80 (£12-£60) for a full 200-rep day. Since the estimate of the company's value at $500 million is based on the idea that it's going to be around for some time, and since the number of views of any much-viewed page is going to increase during that time, a reasonable estimate of the amount of value corresponded to by reputation should be in the higher part of that interval. I would suggest a ratio giving the following figures:
- a 200-rep day gives the company about £40 ($54).
- a rep score of 1000 is for about £200 ($270) worth of work
- a rep score of 100,000 is for about £20000 ($27000) worth of work
(I'd be grateful for some help making a data query for "people reached" against "reputation" points for a bigger sample.)
