Are these physical cards or digital codes?
I'm not sure how easy it is for either to be charged-back, but I put more faith in an unscratched physical card since reading the disclaimer for the digital code, which contains the following:
4. Fraud.
Amazon.com will have the right to close customer accounts and
bill alternative forms of payment if a fraudulently obtained
Amazon.com Gift Card is redeemed and/or used to make purchases
on amazon.com or any of its affiliated websites set forth above.
I've traded BTC for Amazon GCs before, but I dealt with people I trusted.