As is often the case in this world, you get what you pay for. Yes Stewart screens are indeed expensive but I would not use the term "overpriced". Is a Teranex overpriced? I guess it all depends on what it does. Stewart does what it does the best!
Last year, I worried that I might have gone over the top buying a Studiotek 130 electric tentioned screen instead of opting for the cheaper Da-lite model. Having not seen the Da-lite screen, I suspected that just maybe I wasted my money. I was wrong.
I recently did an install using a new Barco Cine 7 and Da-Lite 1.3 Gain (I think it was called cinemavision) Tab Tentioned screen. For the price, it was fine. However, every single aspect of the Studiotek was superior. Most importantly the screen area itself. Contrast, colours and everything else you care to mention look superior on this material.
I use a Barco 808s (8" CRT) and I must tell you, it suits CRT's beautifully. My screen is 87"x49" 1.78-1 which is the exact size (and screen) that fellow forum member TK Chan uses over in Hong Kong. I have seen his G70 throwing onto the Studiotek and it looks even better than mine. (TK uses amongst other things a Fara 3000).
You wont be dissapointed with Da-Lite, but if you want the best, you have to pay up.