(EU only) Apple now offers refunds on digital purchases.

[dig]

Apple now offers 14-day App Store, iTunes refunds in Europe - CNET

Right of cancellation: If you choose to cancel your order, you may do so within 14 days from when you received your receipt without giving any reason, except iTunes Gifts which cannot be refunded once you have redeemed the code.

What this means is that if you regret a purchase within 14 days, EU users have the right to receive a refund after download.

For users in the US, Canada and other countries not protected by the EU's law, Apple can still refuse to refund a purchase and may only issue a refund in select cases like technical issues or failure of delivery. Even then, those complaints are handled on a case-by-case basis through Apple's official support channels.

If you're looking for a refund - https://reportaproblem.apple.com/