Value of complete AR15 upper

[Hastings]

My brother is interested in selling or trading his AR15 upper, and asked me to see what it's rough value is. Its a complete AR-15 upper half in very good condition with a few minor cosmetic scuffs and about 600 rounds through it. I have shot his AR with all of this stuff on it, and it was deadly accurate, but more of a sniper/varmint rig. He is now interested in assembling a shorter, lighter M-4 style AR. Here is the info on what he has.
- 24" Shilen barrel, Stainless Steel, 8:1 twist, .223 wylde chamber
- Bushmaster upper receiver including Bushmaster bolt carrier group with keyed strake and stardard charging handle
- Hogue free float forend with overmolded rubber gripping area
- Del Ton railed gas block

I can post pictures tomorrow, if necessary. What would be a fair asking price for the whole shebang?

 

[12131]

Considering how the AR market has been tanking in the recent months, I wouldn't pay more than $500 for it. And that's generous.