As Roberto and others have pointed out, the auction money is unrelated to the new TLD application money, and it would be wrong for many reasons to turn it into a gift to the applicants.
Calculating the "costs" of the new gTLD program, is very similar to the telecom industry adding new services. Exactly what would be the costs for a particular new service? ...
ICANN has segregated the revenue and costs for the new gTLD program from other costs and expenses all along and breaks them out in their quarterly financial statements, which I presume you have read. You can argue about the details but the general numbers seem accurate. The most recent statement, from last September, says they had $125M left and expect to have $70M when it's over. , I expect give or take defending the inevitable lawsuits from unhappy applicants. There's a separate question of what to do with the extra application money. Personally, I find it hard to have a lot of sympathy for the dire conditions of speculators and marketers who applied, and I'd treat the extra the same way as the auction money, use it to support projects relevant to ICANN's charitable mission. Regards, John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies", Please consider the environment before reading this e-mail. https://jl.ly