A storm chasing friend of mine collects the insulators. While we were in New Mexico last spring, he walked along the old Santa Fe looking for some insulators.
He said that some can be quite rare and quite expensive when buying them in the clubs.
I have a couple of old ones from the Boston & Maine Railroad. When the MBTA was redoing the line, they took out the old poles and the insulators were lying around. There were a lot of broken ones unfortunately, but I found two that were in excellent shape. They are probably over 100 years old.
John