betting formula.

Hey i need help deciding a formula for me and donny's new website. Basically lets say you have two teams:

Orlando Magic and LA Lakers (NBA finals anyone :P)

now lets suppose you are to bet on it. Lets suppose your team won. How would you calculate your payout?

right now this is what I have:

A ratio or 1:2 on the Lakers side.
Suppose you bet 100 on the lakers.
Suppose the pot is 500 total.

If you win, your payout would be 500 + 2 * 100 = 700. If you lose, your payout would be 0.

Is this a good way to do it? the only downside i see is I dont/want to analyze statistics on each team to get a "Ratio" between two of them. is there any easier method to do it?