I suggest bringing a cooler full of ice. Buy early so they don't run out of the size/s you're looking for. Throw them in the cooler and go back in and enjoy the expo.

The prices will vary, so you'll have to see who will be there and go from there.

Taxes, I'm not sure, possibly varies state to state. There was no tax when I purchased in NH, but I don't know other than that.

Cash rules, you know they'll take cash, so might as well bring it. Though, cards are accepted at some booths.