How much would it cost to produce Wikipedia?

Jussi-Ville Heiskanen said, on wikien-l, that "No amount of donations could have payed people to write our content." I'm not sure in what sense that statement can be taken seriously, but it raises an interesting question which I've thought about before - how much would it cost to produce Wikipedia?

Clay Shirky estimates that Wikipedia "represents something like the cumulation of 100 million hours of human thought." I'd be interested in seeing a derivation of that number, but assuming it's correct, it puts an upper bound on the cost to produce Wikipedia on the order of $2 billion or so, right? (Figure $10/hour for amateur labor and then double it for overhead.) Compare this to the $5 billion valuation Jason Calacanis gave to the project for a little bit of fun speculation.

But I think Wikipedia could have been created for a lot cheaper than that. Working down from Shirky's 100 million hours, you have to figure a large portion of that time was wasted on things like fighting vandalism, edit warring over silly issues, or trying to find a reference after the fact instead of including your sources from the beginning. Now I'm not sure if Shirky's figures include all the work in the meta namespace. If so, that's a huge chunk of wasted time there. If not, that's probably some partially useful time that has to be added. But this assumes hiring lots of amateur writers is the cheapest way to create a huge, but mediocre, encyclopedia. I seriously doubt that's the case. Who would write more articles, 10 amateurs working 10 hours each for $10/hour or 5 professional writers working 5 hours each for $40/hour? I'm guessing the latter.

But let's approach it from the other end. Using an old figure of 435 words per article, rounded up to 500, and 2.5 million articles, we're talking about 1.25 billion words, or a mere 12.5 words per hour (and that includes rambot articles). Surely a large but mediocre encyclopedia can be written faster than that. Amateurs writing at 125 words per hour for $10/hour or professionals writing at 500 words per hour for $40/hour could create Wikipedia for a mere $100 million.

For a third approach, Mahalo is paying $10-15 for a 300 word search result page. So at that rate we're talking about $40-60 million or so for 1.25 billion words.

Somewhere between $100 million and $250 million seems about right. What do you think?