Can anyone tell me why the Gov't Carbine R6520 lower would cost $1900?

I am looking at buying a complete M4 from this guy, and he says he has $1900 into the lower. $750 in the upper, which is marked cmp 5.56 NATO with a  1/7 twist rate barrel, that he says is from a post ban M4 machine gun.
Is there anything I can ask him that will help me verify that I am not getting taken here?
Serial number of the lower is GC0093XX.
Total price is $3000 with some accessories.

Thanks in advance... db

seems  high to me. A lower in that serial number range should have a sear block and raised fence around the mag release button. I can see higher prices for lowers with the fence and WITHOUT the block, but he is high.

Thanks. . .I should have added this info too I guess...He says the sear block was removed by Lauer's Custom weaponry, and that it has the raised fence as well as M4 feed ramp, and Dura Coat to match the upper with a Phantom flash hider pinned on the upper. . .db