Couple of problems:
1) 30% overhead!
2) The transactions are often backed by credit cards, so there is a long list of things that aren't allowed. See the last one:
https://support.google.com/payments/answer/75724It may be that you could do it for a while, but it's unclear that it'd be sustainable.
Agreed. 30% + Exchange Fees + Your Profit = 35%-40% above exchange rates. Even if it got accepted into the store your app would get shut down quickly.