The ones I have seen similar to that are going around the $600-$700 range MINUS the BCG.
Yeah, there's no way in hell I would ever pay that price. I'm just saying, it someone wants it now, then that's what they are paying just to get their hands on one.You can get BCM uppers minus the BCG and charging handle for $450 -529. You just need to keep an eye on their site. Whoever is paying $700 for a bushmaster upper is desparate and doesn't know what they are doing.
With that said, you could probably easilly sell it to someone who doesn't know any better for $700-800 because you have a BCG with it and people are buying anything now a days.