Why did Sydney feel that he was entitled to $1,700 of Billy's money?

In White Men Can't Jump, Billy hustles Sydney in a basketball game for $64 in the beginning of the film. Sydney finds Billy after the game to strike up a partnership to hustle basketball courts in the area to make extra cash.

Billy gives Sydney $1,700 of his own money to bet on a game that they plan on hustling together. After Billy and Sydney lose the game, it is revealed that Sydney double crossed Billy to keep Billy's money.

When Billy and his girlfriend show up to Sydney's home to demand the money back, Sydney tells them that he had to get his money back.

Sydney: No, baby. I didn't steal his money, I hustled his money. That man hustled me long before I ever hustled him.

Billy: You fucked me, man! You fucked me! We had a partnership!

Sydney: Had to get my money back.

Was there ever an explanation as to why Sydney took so much more money from Billy if he only wanted his original money back?

Billy originally only hustled $64 from Sydney before they ever knew each other. There is a huge difference between $64 and $1,700.

What was the reason for the immense variance in the money that Sydney felt that he was entitled to?