I would expect that increasing the working lifetime of one of the people in question by ~4 years is worth way more than $100k
It is certainly a possibility worth testing using a properly designed metric.
(And that's ignoring the indirect effects: if one of the runner-up 24 decides to skip college and launch a startup without taking Thiel's money as a result of this offer, that's a win for Thiel, even though it would look the opposite in the metric you're proposing.)
Or get discouraged by the loss and go into finance to work as a quant, or something similarly useless to society.
Peter Thiel is offering another round of "20 under 20" Fellowships. The application deadline is December 31st. We know many of the current Thiel fellows here in the Bay Area, and it's a great opportunity. Here's the official letter from the Thiel Foundation: