All of the low cost acoustically transparent screens are woven fabric vs micro perf vinyl. $700 is a lot of money to spend on fabric that may also deteriorate the image. Even more when you consider you only get a couple years of warranty - which is not something I would want on an electric screen.
But $700 is a lot less than what the big names are charging. There is a 3x-4x multiple on brand name vs Internet Direct prices, electric would be even more - but the warranty is much longer, too.
I am a DIYer, so where I did not pay for a fancy screen (Stewart Cima Perforado for 2nd theater), I sanded and painted a wall - and my latest attempt (I sanded like crazy) the wall appears to be perfectly flat. Just normal valspar paint and primer and a roller, and a lot of sanding.
So that's my perspective, I'm willing to do a good bit of work to make my own screen, but for AT screens, they just are expensive, period. Adding in electric rollers, and you are really talking about a very premium product.
$700 is a lot of money to spend on fabric.