Estimates vary wildly from $100,000/year to $1.4 million/year http://en.wikipedia.org/wiki/The_Pirate_Bay#Funding That's about $270/day to $3,800/day, although some of that is private funding as well as advertising.

That $100k is from 6 years ago .. so 6 years ago their lawyers admitted the site made (at least) $270/day and today it does probably at least one order of magnitude more traffic.