Depending on what card you have, it may make more sense to buy the amazon gift cards with an Amex and then use points to pay for your purchase. For example, with the Canadian biz platinum card, I could spend $700 to buy the gift cards and then use 70K points to pay for the purchase (instead of using 100K using amazon's shop with points). But, different cards have different rules (the Canadian gold card would take 100K either way). I'm not sure what the rules are for US cards, but it may be worth looking at options.