The answer to this question is "Whatever someone is willing to pay". To a mechanic they are worth the cost of a used set of drivers. To a collector they are worth 4x that.
Best awnser of the day.
"Whatever someone is wiling to pay"
I owned an antique mall for years and once had to go to court to give the value of some items in dispute. The person payed way to much for things and wanted their money back. In the second hand business you don't give returns. If something goes bad you you just figure you made a bad deal and move on. I have had it happen many times but not often and it is nothing when you figure I have bought out a few million dollars worth of things in my life.
Well back to the story. The judge asked me to state a value. I had nothing do to with the case. I told the judge that the value was what anyone was willing to pay at any given time. I gave my estimate and stated a value and the judge aske me how I cam up with that price. I told him because I have sold like things for said amount. I said I could have gotten more but wanted to turn over my merchandice. I also said that I have payed far to much for things myself. I always figure if I am dumb enough to buy it and think it is a good deal someone else will if I can't sell it for a profit. 99 percent of the time I am right.
The judge rulled that the merchandice was not defective and that both parties argreed on the selling price and that there was no false representation.
The judge rulled in favor of the seller and told the buyer to research what he was buying ahead of time.
E bay is crazy. I pick off things all the time. Some crowsfoot go for $50 and the next week the set will bring $120 You never know. If you never pay more than 24% of the retail price you will always do fine. You might not always make any money buy you will not loose. I don't buy unless it is under 15% and I do it every week with tools. I buye $125 wrenches all the time for around $7 and they are not full of rust ither.