Really depends who wants them. Could be from $50-$350. Same as D0VE, as I'm sure you know.
A guy restoring a 1968 Lincoln would need period correct C8VE-A's or C8VE-E's and might pay a pretty penny for them. On the flipside, with all the aluminum heads becoming available and unfortunately some of which are JUNK and therefore inexpensive, the early iron castings start to look like they have less value. The joke about this is that the cheapo aluminum heads offer little power improvement over the classic factory iron in many cases. Also, guys running a race class that requires factory iron will pay for a quality set of original castings, such as a truck puller. And then there are guys that love to pop the hood and show what appears to be a factory iron 466 and then smoke the competition with what is really a 521 under the hood.
Generally and from a performance standpoint, I personally feel that a 30-year old pair of true virgin iron castings (C8, C9 or D0) that haven't even had the seats cut since the factory hold their value...absolutely. To me, they're a blank canvas capable of outstanding HP for most of the builds we do over here. Were you closer, Blown, I'd get them from you myself. We retail them for $289 outright (bare, cleaned and blasted), but usually give a substantial discount when they are purchased with a port job/where we provide the entire cylinder head assemblies fully reworked and ready to bolt on.
LO