Apologies for my usual obtuseness but I'm not sure I get the downside the $1000 limit. If I understand, that is if using 2 gift cards for one transaction?

With 2 methods of payment allowed, one could use 1 gift card and 1 credit card for a transaction of any amount, so if one were to buy 4 gift cards and use them on 4 trips, they would benefit fully from the $200 added value with only the holding costs of the value of the gift cards to cover.

Am I missing something?

NB: Asking for a friend as I deplore Costco more than I deplore carry on baggage.