Yes, but you do know what I am saying. I can go to my sdb today and pull out 20 1942d VG WL halves. Every one might be "unique", but are worth identical. Now try pulling out 20 error coins and tell me they are identically priced. Unless it's a die error you cannot. Something like brockages, off center strikes, or similar all will have various difference that can affect value. Maybe some off centers are less offcenter, or a couple do not have sates, etc. That is what I meant, there is not enough volume of them to create a true market price, only a generalization. So yes, while every coin is unique most unique features do not affect value. With error coins, though, every unique feature does affect value. Therefor, they are much harder to value IMHO. The first sentence might be an over simplification, but so is just saying "the market", especially for somewhat unique items that do not have deep markets. What is the value of a 50% off center, 1853 arrows and rays quarter in vf? Whatever one buyer and one seller agree on. Please tell me what "market" is applicable.
I didn't say I disagreed with what you said about the pricing of errors Chris. I was merely pointing out that every coin is unique - and not just errors. And yeah, what you said about a '42-D Walker in VG may well be true, probably is. But go look at realized prices for one in MS65 and I'll bet you find them all over the map. With one or two being double the others - and that is because they are each unique.
Which is why some of us are trying to get away from the term PMD Post Mint(ing) Damage and instead are using PSD Post Strike Damage.