I am not an expert in many things, but one of the things I am an expert in is the Captain Marvel comics published by Fawcett Publications from 1940-1952. I collected them obsessively for years and learned everything I could. The holy grail of the Fawcett comics collector is Whiz Comics #1 (also known as #2, but let's not worry about that now!).
In the 1970's DC Comics, having purchased the rights to the then defunct Fawcett characters, release a series of reprints, including Whiz #1. These were nearly exect reprints, except for the fact they were larger than the originals, had a different paper quality, and came inside an cardboard outer cover. The outer cover had all the info about it being a reprint; without the outer cover, the comic was and exact copy of the original. As a result, many people mistook these for originals, or deliberately remove the outer cover and passed them off as original to uneducated buyers. Value of the original, depending on condition, could be well upward of $10,000; the reprint, without the outer cover, maybe a buck.
A couple of years ago, I saw an ebay seller offering the reprint of Whiz #1 as the original. There are actually several ways to identify the reprint, the easiest being that the words "Make Way for Captain Marvel" which appeared on the original were deleted for the reprint, due to a trademark conflict with Marvel Comics. I pointed out to the seller that he was in error, offering it as an original, assuming he just didn't know. He responded with an angry tirade telling me I didn't know what I was talking about. I responded with dozens of sites documenting the differences. He responded angrily again, telling me this was a "special edition" of the original and that's why it was different. It became increasingly clear that he was either willfully ignorant, or was deliberately fraudulent. As it happened the issue was bid up to nearly $500, an absurd price for the reprint. I notified ebay, but as far as I know, they took no action.