So you are basically saying that there is a 10% service charge yet the cashback the users will have will be 30-50% of the value of their purchases? Sounds mathematically impossible for me in terms of all parties having profit in a sense.
You forget the temporal component, silly Theb...
Income = 10% today
Expenses = 50%
in 2-4 weeksObviously when growth plateaus and expenses bypass income, the ponzi collapses.