Seems reasonable to me. It's at least a good jumping off point to start negotiations. [:D]
On a personal note. I have a preban PWA lower and I love it! I have it mated to a Bushmaster M4 upper and it is my "daily shooter" gun. It has seen many thousands of rounds and functions flawlessly. The finish is very durable and the upper and lower fit together tighter than any of my factory Colt guns. If I had the money I'd snatch this lower up from you right now.
[Hope that helps sell it for ya']