Here's and example:
Bought Colt Model R6601 the day after Christmas for $1000, with 1346 rds of ammo, 8 stripper clips, ammo can, Owner's Manual, after market sling, 2 5/20 rd Colt mags, 2 30 rd OKay Mag, and SKS Nylon Case. No BOX.
Sold the 2 Colt mags for $68, and the upper for $475.
Installed complete Colt 20" 1/7 A2 upper (with A2 Compensator and Bayonet Lug) and standard push pin I already had. Figure I'm into it for $480, not including the parts I already had.
Just yesterday, someone offered me a pre-ban Bushmaster for $1000.
Earlier this year, I had another oportunity to by a pre-ban for $900.