Price estimate for barely used Edel. Perf. RPM alum. heads w/ 2.02/1.60 valves??

I want to sell the aluminum Edelbrock Performer RPM cylinder heads that are currently on my '90GT. The part# of the heads is #6025, and they have the 2.02/1.60 valves with studs & guide plates. I have an aquaintence on another stang site that wants to buy them...but I'm having trouble deciding on what to charge him. I want to put a few hundred along with the money I get for my heads and upgrade to some AFRs. My Edelbrock heads are currently on my healthy, good running rebuilt 306 and are in great condition. The heads only have 20K miles on them. Let me know what you guys think. These same heads are going for $1,059 from Summit. Thanks in advance.