It’s often possible to buy discounted GameStop gift cards through different sales. The reason why they
are were popular is because GameStop sells Amazon gift cards, which are rarely discounted anywhere. And many locations allowed you to purchase Amazon gift cards with GameStop gift cards, hence giving you a nice discount on Amazon purchases.
That seems to have all ended. Gamestop stores are no longer allowed to accept their own gift cards for Amazon gift card purchases. Registers have been hardcoded to block these transactions. Apparently Amazon cash has also been blocked.
HT: Miles per Day