WSOP 2012 ended a week ago. The winner was 
Greg Mersonwho won $8’531’853... American financier, Las Vegas tax consultant - Russ Fox reported in his blog that the winner received almost half the amount, namely - $4’838’327, after all taxes.
Merson paid three taxes - to the pension fund $247'424 (as a professional poker player who does not work anywhere), to the tax office of his native state of Maryland $469'252 and to the US Internal Revenue Service $2'976'850. Thus, the WSOP champion lost $3'693'526, which is 43%.
Prize money 
Andras Koroknai took home in full. And even in his homeland, his winnings have not diminished, since there are no taxes on gambling in Hungary. Thus, the Hungarian, if we take into account the prize money, is ranked higher.
2012 WSOP Main Event Final Table After Tax Prizes:
1 place - Greg Merson + $4’838’327 (-$3’693’526, -43%)
2nd place - Jesse sylvia + $3’327’973 (-$1’967’176, -37%)
3rd place - Jacob balsiger + $2’379’932 (-$1’419’141, -37%)
4th place - Jeremy Ausmus + $1’758’174 (-$1’093’363, -38%)
5th place - Russell Thomas + $1’369’761 (-$785’552, -36%)
6th place - Andras Koroknai + $1’640’902
7th place - Michael Esposito + $839’861 (-$418’479, -33%)
8th place - Robert salaburu + $622’156 (-$349’042, -36%)
9th place - Steven gee + $452’543 (-$302’255, -40%)
In total, from the prize money played only at the final table, the US treasury received - $10'028'396.
English 
Russian