Generally no, not everything can be returned within a short period of time. Have you not seen "all sales final" on a receipt? Doesn't matter if you changed your mind one hour or one day later, the store does not have to accept the merchandise back for refund or credit.

We can debate the amount and or fairness of Avis's fees, but the fact remains based upon your reservation a vehicle was taken out of availability. Since locations only have a finite number cancellation fees can be seen as a way to deter persons from making reservations they may or may not honor.

Why not just call Avis and ask to have the fee waived?