What if they charged you a "hefty" one time fee, and then every month that passed, they gave you back a % of that fee, until you got a match? Their incentives

What if they charged you a "hefty" one time fee, and then every month that passed, they gave you back a % of that fee, until you got a match? Their incentives will then be aligned. The problem there will be to know when someone got a match.