We were getting requests to pay docker a lot of money because of the volume of docker pulls we were doing. We used a pull-through cache on DO as a work around and its a been a big success.
My colleague wrote up a guide to pull-through caching dockerhub.[1] Docker's pricing is a little bit funky, because a full image pull with all the layers costs the same as a request where you retrieve no layers at all.
If this AWS feature were out a couple months ago and had support for dockerhub, I'm not sure we would have set this up.