price on nos part

 What would be a fair price to offer for a pair of NOS Bugeye rear bumpers?
I have a line on a set but the seller is like an EBay auctioneer - he want's 
an offer, and I've already tried the "Well, I'll give you $10/20/50 for the 
pair, now what do you want and what will you take....?  He just gave me the 
"make me an offer that won't insult me" routine three times. They  are 
unrusted, and as I bought a truckload of NOS stuff from the same source 10 
years ago, I'm sure these are the real thing.  Mark