Yep.
I can only speak for myself, but I wouldn't pay anything for a Xerox copy, whenever the copy was made.
I even shied away from the signed post-70's Bukowski manuscripts that were Xerox copies. Even though the copy has an original signature, they don't have the same significance - to me - that an original or a carbon copy does. Maybe the distinction between carbon and Xerox is stupid, after all, they are both mechanical reproductions of the original. But the carbon being in his typewriter makes a difference to me.
But a copy of a letter or a manuscript without an original signature is worthless because it is infinitely copy-able. I know some have sold on eBay for $50 or whatever price, but unless there was some personal significance to the letter, and there was no way to get the original, I don't understand paying any more than postage costs for a Xerox.