Smith and Wesson M&P 15 Piston- Below dealer cost
I just ran across this, thought I would pass it along, as it seems VERY reasonable for a piston AR (if that's what floats your boat)
Smith & Wesson M&P15PS Piston Driven 
(the below dealer cost is their claim when they put it on facebook)
"In Vermont authenticity is all, they do not try to keep it real, they are real."- NY Times.