Thanks for the heads up, that's the cheapest price for a piston AR I've ever seen! I'm not interested myself but bet they won't last long.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek