Return an apps?

You don't.

All sales are final

Not true there is a a way

Could you let us know what it is? In Australia, the law says that if you make a purchase and it doesn't work or is faulty or is not fit for the purpose you bought it for, then the seller must either replace it or if that is not possible, to refund the cost. I don't know what the law is in other countries, relating to returns.

If you've just bought the app and it's not working as described then use the 'report a problem' page to contact iTunes Support : http://reportaproblem.apple.com