I have never bought a card on Amazon as I have noticed the same prices you have. I say you get the $600 Home Depot gift card and sell it or trade it. See #3:
https://www.moneytalksnews.com/6-tip...ft-card-scams/
The first site shows that you can trade the $600 HD card for $510 on Ebay, so you can buy the card at $350 and have money left over for another card.
Note: I have never used either site in that article, I just know that this sort of thing can be done.