If theyre making you happy with their production, give them popcorn as a treat...they go absolutely insane for it.
I give them any veggies that we have that are going bad, and at one point I gave them the rinds and core from a pineapple, they enjoyed that for a bit.
For the OP
Pricing, you got a good deal BTW. I sell trios for like 30 bucks cause I find that Im one of the few locally that has ASFs, and quality ones at that. The local pet store has them for like 5 bucks a piece but they only sell males, I sell feeders for 1-2 a piece.