Hello Moneysearch4u,
rev share works on the revenue generated for the merchant by you on a monthly basis.
So in your scenario where a player loses 50€ (making money for your merchant) but then wins 80€, your revenue would be calculated on the total, -30€. So no commission.
Another similar scenario is where one of your players loses 50€ and the other wins 80€, same principle, the wins negate the losses and wipe out your commission.
This is usually on a per month basis (unless your affiliate program carries over negative revenue, something you need to check out when selecting a program). So, if on Nov. 30 you have totaled 50€ of revenue for your merchant but all of a sudden on Dec. 1 your player wins 80€, you should still get commission for November because you generated positive revenue for that month. Does that make sense?
Lastly, many affiliates make a very good amount of money on rev share with casinos because their players often end up losing. Much more than in sport-betting, for instance.
Lluc.