As I said, the equation is simple, we just need a dollar value for the points that a person invests in the tournament.

If you had to guess, what is the conversion of 140 points to dollars? Looking at your redeem cost (580=$1 Carbon) that would make an opt-in cost about $.25.

So, the equation would probably be total winnings/(total opt-ins*.25)=ROI

I would probably suggest setting a minimum number of tournaments to qualify. Say 5/week or 20 tournaments to qualify for the monthly leaderboard?