What are these tires worth?
 

On my '77 Corvette I have a set of Goodyear Eagle ST's that are in good condition. I know these are no longer made and many people have told me they are worth something. I've gotten people saying anywhere from $200-$800 a tire. I don't plan on selling these, but saving them for show. I'm just curious as to how much someone would really pay for these. I've looked around the net and cannot find ST's in this size. I think it's 255R15. The one's I see are nowhere near as wide as mine.
Thanks.