Last year I bought that model of lower for $157, shipped. Turns out the lower was a gateway.
I had previously bought a Glock 19 (Gen 4) pistol. I think I was the last member on ARFCOM to buy a Glock. I wanted to have another gun to share magazines, so the AR9 lower project gun was chosen to perform that duty.
With the lower as the start, I added an NFA upper with LRBHO ($233), 16" barrel ($110), gas block with top rail, single feed bolt/carrier group ($115), LPK and stock ($109), 9 mm (two-piece steel) buffer ($30), four more Glock 19 15 round mags plus one 33 rounder and a mag loader ($105; all mags, for pistol as well as AR9, are factory), low cost ($50) dot sight, low cost ($26) back up fold-down sights, thread protector - not flash hider ($8), carry case, etc. All totaled, including the $2 in quarters in the buffer tube to reduce bolt travel, I believe I have spent $1050 (all prices include shipping, not all parts and costs shown) on the project.
After a minor tweak to the LRBHO trip, everything works as expected. It's just another AR9, so no bandwidth wasted on pics.
Was it worth $1050? While it's a nice shooting, accurate carbine, had I known what the total cost would end up, I'm not sure that I'd do it again.
MHO, YMMV, etc.