It's a good idea but any cut above this will make the lottery very expensive. National lotteries can pay out 50% because they have a monopoly and the remainder usually goes towards a community project.
I will probably increase fees (nothing to exorbitant) to covers costs if this takes off. I don't think it will require to much to run unless it becomes insanely popular. At that time, I will open up more lotteries for different payout ranges to make it more beneficial for costs.