My tournaments range in number of players (have only been doing it a couple months, so the "regulars" are still growing). Right now, I pay out like this:
8 players or less:
1st Place: 65%
2nd Place: 35%
9 Players or more:
1st Place: 60%
2nd Place: 30%
3rd Place: 10%
The buy in is $20. And I always make a "rough" round to those figures, so everything comes to an even $5 or $10 divisible number (it's hard enough to get people to bring $5s and $10s instead of just a $20... if I started paying out to the dollar, I'd have to set up a bank at my house). However, since it IS a rough round, I let everyone know what the payouts are going to be BEFORE the game is started. That way, if I place 2nd or something, nobody things I'm rounding in my favor.
Plus, at $20, even at 9 players, the 3rd place person breaks even. I don't pay out anything under break even.