Quoted:
Bought my first AR-15 a short time ago.  Started looking at building my own.  This caught my eye––http://www.gunbroker.com/Auction/ViewItem.asp?Item=117973285.
The price blew me away.  What did I miss in valuing this upper?[/div]

You missed the hysteria.

$1,200 for a DPMS upper.

Uppers are in short supply right now, but that is ridiculous. I just saw several good deals on the EE just now that beat the hell out of this.