But actually Black Market DOES effectively give you extra buys. I'm not sure that people get this. When you buy a card from the BM deck, you've bought a card without using a buy - effectively a limited extra buy, but here, so long as you've played your goons first, it's as good. And with 100s of cards in BM, Fairgrounds can get pretty ridiculous actually methinks.
You won't be able to do that on isotropic though.