$250 seems high to me for an Expert in that condition, but it may depend on pricing trends in your area.

Here in Texas I paid something like $200-$220 for an '89 Expert in excellent condition with, as far as I could tell, all original Suntour GPX group components including the Suntour chain. Original white hoods are still in great shape. Only the tires were non-original -- new and decent not great Vittoria Zaffiros. The bike was ride-worthy as-is and I did so for months before replacing the tires. A little at a time I've replaced or swapped parts around -- cables and housings, brake pads (the original Suntour pads were still good after decades), freewheel (I like SunRace chromed 13-25 and 13-28, I think it's the MFR30 and MFM30), and Vuelta chainrings, 50/39 and 38, just for easier climbing without sacrificing much top end speed other than on downhills.

BTW, the Suntour chain was definitely not one of their highlights and I quickly replaced it. But I cleaned and waxed the Suntour chain for posterity. It's in a ziplock bag for ... whatever. Might give it to a friend or collector who happens to want it. I mostly use KMC chains.

And a year later the same fellow I bought it from had another identical Ironman in even better shape for only $200. I hemmed and hawed and hesitated and it was gone by the time I made up my mind to buy it. Kicking myself over letting that one go.

When I see an Ironman for sale in Dallas to our east they sometimes ask higher prices, but I'd be surprised if anyone actually pays $300-$500. There's no shortage of good 1980s steel road bikes here and Centurion isn't in as much demand as Trek and other more familiar names. I also see some Diamondback road bikes from the early 1990s, nearly identical to the Centurions although the frames reportedly weren't quite as nice. Those Diamondbacks usually sell for $200 or less even in top notch condition. I've considered getting one just to dedicate to indoor trainer use.