Merch?

I don't remember their being any last year but maybe I'm crazy...You will most definitely find food, beer, and posters though. So as far as merchandise goes their are posters and (maybe) t-shirts. Last year all the vending was between the blue and orange stage (someone correct me if I'm wrong). But they haven't released the festival map this year so it's a question for me too...either way the merch they do sell won't be hard to find I assure you.
The robots are nothing, if not versatile.

Last year there was merch at the top of the hill and inbetween the black and orange stages (headliners merch). Plus, there will be all sorts of awesome Austin vendors around the main entance/food court area. Like Warped, the bands will be selling stuff cheap, so cash is a good idea. You will also find some swag. Seriously, FFF rules.

Depends on the band. Some of the bands will sell you stuff at club show prices, The headliners might be a little more. I forget how much the festival shirts were in previous years, I'm thinking around $15. Much more reasonable then other fests. Last year, they also had a really cool deal where they will print you a shirt right on the one off your back for 5 or 10 bucks. Not sure if they are doing that this year.