Palmetto state armory has ar pistol kits around roughly 300 bucks or so.
"The Askari, which conceals well in an average backpack, is a 5.56 AR pistol platform with 7075 T6 forged aluminum upper and lower ambidextrous bolt catch and release. It also features a 7.5-inch 1:7-twist SEP match barrel with a 4150V-grade Mil-Spec B 1159E chrome moly (CrMo V) and black nitride finish-NiB barrel extension. The pistol-length gas system with Geissele .750-inch low-profile gas block comes complete with a 7-inch Geissele MK 14 Rail System, Geissele airborne charging handle and Geissele carbine buffer and 42 wire carbine buffer spring. Other accoutrements to be found on the Askari include an AAC Flash Hider, WMD Nib M16 BCG, Radian 45-degree ambidextrous safety, Law Tactical folding adapter SB SBA3 Pistol brace, VZ Grips AR Grips, rail panels and hand stop, and Magpul Pro back and front flip-up sights complete with Magpul Trigger guard. Read the rest of Askari AR pistol.
Yeah, $300 for an AR upper assembly. This list of custom whiz-bang stuff goes on and on and on for so long that you've gotta go to his website to find the end of it.