Am I doing this math wrong?

The poker room I use has sit and go double up tournaments.  10 player tournaments where the top 5 double up and bottom 5 lose. 

Lets say I turn it into a 4 game chase.

game 1: $5 to win $10 ($9.65 profit after rake)
game 2: $10 to win $20 ($13.95 profit after combined rake)
game 3: $15 to win $30 (12.95 profit after combined rake)
game 4: $25 to win $50 ($16.20 profit after combined rake)
Loss = -$55 (-$58.80 after combined rake)

So if I lose game 1, I move to game 2, if I lose game 2, move to game 3, ect...  Lets say I can maintain just a 50/50 winning percentage per tournament,  Mathematically I would have a 93.75% chance of winning the chase.  Lets say I play under .500 and win the chases at a 90% rate.  That would still equal a estimated $465 profit over 100 chases.  Am I doing any of this math wrong because this seems like either a miscalculation on my part or easy money.

I have not checked anything else buy your initial profit from the $5 dollar game is $4.65, not $9.65 (Profit = Total - entry).

You are then risking $10 to win 20, so Total Profit= 20- 10+5 = ~5 without considering rake.

ok, yeah.  I'm an idiot.

sorry i gotta laugh

ok there it is i knew i had one in me