Apple does not have a straightforward way to get a refund on a paid app. But if iOS users "Report a problem" with a purchased app, one of the options is a refund.
This opening has now been slammed shut by Apple. There is no word on how much money developers refunded over the years to users of an app, who then reinstalled and updated it as though they never received the refund in the first place. It doesn't seem that you could, or even should, blame Apple for getting rid of an opening like this, which should have been hammered shut a long time ago.
Apple closes the window on free paid apps for iOS users
source: @macguitar via MacRumors