this is supposedly no-fee, at least for now. gift cards are quite the scam, i think the standard is a $4.99 fee for cards under $100.
General purpose visa/mastercard gift cards yes, but single-company gift cards just cost face-value (or sometimes slightly discounted at places like Sam's). And some of the participating stores like CVS already sell Amazon gift cards.
I think you may be thinking of Amex and Visa gift cards. AFAIK, those are the only ones that charge any sort of fee. Amazon, and other retailers, eTailers, restaurants, etc., generally don't have a fee to buy or maintain, and funds never expire.