Mark-up should not be front-loaded. It should come off as a discount AFTER the player cashes. This means the player has to cash to make money. And the deeper he runs, the more he wins. So he will have an incentive to play well. Also, by back-loading it, it removes the ability to scam players by selling more than 100% and then intentionally busting out before making the money.
So instead of paying 1.2 markup up from for 100% of a players action, where the player locks in a gain of $200 for a $1k event and the backer will lose $1200 if player does not cash, instead charge 100% or 1k and backer only loses $1k max. but will then get 80% of net profit. So if the player cashes for $6k, the player wins $1,000, not $200, and player wins $4,000 net.
For randoms, friends, and 95% of all tournament players, 90% to 95% should be the payback for the back end to the backer. Only top pros deserve 80% to backers. (ie 20% to the player).