The gun store here is pre selling the LEO Colts for pick up on the 14th for $1049 plus tax which would put them at $1146. That is for the M4 with collapsible stock and detachable handle. He has col stock DPMS whole guns for $699.
So 70% of the price of a new Colt M4 is $802. So it looks like a clean factory pre ban Colt with box, mags, etc would go for about $800. Prices will go down from there for beaters or Frankenguns. Less too for 20" guns with fixed stocks since everybody wants shortys. I can remember the time between the passage of the ban and it being signed. Guys were standing in line to pay $2500 for Govt Carbines.
I'm only going to loose money on one gun. A NIB Lightweight Sporter factory drilled for push pins. I sold a green label 20" to get it, but I didn't have anything in that one. I am happy to eat it. To all the guys who were too young to get stuff before the ban GET WHAT YOU WANT NOW.
Get on a program of buying 2 mags every payday or something and buy one rifle a year and just stack them up. You won't be sorry. I wasn't!