bad9 I used to do a lot of picking/reselling on Ebay, of older iron sets. True, not all are collectible, and actually very few are wanted unless they are #1...in excellent condition #2....in not so excellent condition, but the buyer at least wants a set of them until they can find that excellent set.
Wilson, MacGregor, Hogan and H&B are basically the top sought after, esp. with all irons/woods in the set. There are those out there that will collect the 'oddball' brands/clubs, but not so many as the others. There are putter collectors out there also, and will pay disgusting...obscene amounts of $$ for certain clubs.
Then again, it's all a matter of "want", in the mind of any buyer. And if more than 1 buyer "wants", you can get lucky sometimes.