Some of those may be local to me only so YMMV, but just call around to all the sign shops local to you and go with whoever is going to give you the best price. I usually have to pay $30 for a sheet, and they charge me $5 per cut, just to make a simple cut and cut it in half!
Curious to the OP, where did you find you could get a sheet for $20? Whats the store name?
And some places are total a-holes, one place quoted me $130 for a blank sheet, no doubt trying to toss a $100 profit margin on top for them, bah!
This guy was FOS. When I tried to get back with him he was, conveniently, never available.
I ended up going to another place in Hamilton, Ohio, (I can't think of the name right now) and got a sheet for 40.00 and they cut it for free. They were really cool about it too. They said they didn't usually carry it and special ordered it for me. They even carried it out to my car for me.
I still have about three quarters of the sheet left this stuff seems to go a long way. I love working with it. I've already got ideas flying around my head about what to make with it. One thing I'm gonna try is to make a Slave Leia bikini top for my wife with it. I used super flex sculpey and I dont like how it turned out.
I,m currently getting started with a couple of scratchbuild projects and the cheapest sintra I can find at any sign shop near me is $52 per 4x8 sheet. I've checked all the shops and that seems to be the standard rate. I live in a decent size city in the southeast U.S. ,so supply shouldn't be a problem. Why am I paying double for this stuff!