its not so easy like you mentioned , you forgot to mention the big part SCAM 
Trade 50$ worth of BTC for 100$ AGC [ Scam happens 90% of the time when this rate followed ]
Result :
Your Amazon account being fucked for having invalid AGC , your 50$ BTC which you paid for that AGC fucked
So its not easy like you mentioned , it has huge potential of being scammed .
Trade 50$ worth of BTC for 100$ AGC [ Scam happens 90% of the time when this rate followed ]
Result :
Your Amazon account being fucked for having invalid AGC , your 50$ BTC which you paid for that AGC fucked
So its not easy like you mentioned , it has huge potential of being scammed .
I think there are ways this can be done, but with too much carefulness.
I have seen people trading their fiat or bitcoins for Amazon Gift Cards, but the only ones which are physical or purchased through cash or credit cards from a store. There are very less chances of getting scammed in these cases, unless you go for e-codes where possibilities are, you go first and pay and you get something which has already been used or invalid, so that's what we need to remain safe from.
even if that Physical AGC . But its also true that Physical card with cash receipt lowers the risk a lot but you have to be sure that receipt is not photoshopped ; its definitely not easy like op mentioned it carry some risk of course .