math help please, Charity tourney

[hyde]

Prizes are 65% of intake...that's the charity part

Players start with $3000 in chips
One anytime buy in for $35 and $1500 in chips
Preregister and get an extra $500 in chips

So I'm planning on the immediate anytime buy. And I assume most players will.

But here is my question, how much of a mathamatical disadvantage am I at by not pre registering and getting the extra 500 chips?
Is it as simple as 10%?