eBay gift cards do not normally earn cash back through portals, however Doctor of Credit is reporting that Ebates is currently paying 5% back for their purchase. (If you don’t already have an Ebates account, you can find a signup link for Ebates and many other cool things here.)
It may also be possible to earn 5x points with the Chase Ink card when purchasing these cards. Combining portal cash back and credit card rewards can result in a significant savings on eBay purchases.
To find out how to maximize this deal and for the latest developments, see this Doctor of Credit post.