"These people who are selling these things, I'm sure they're not doing with intent to hurt anyone, but they don't realize they're profiting off of our nightmares, our misery, our agony," Thompson said. "That's just wrong."

It is against the law for convicted criminals to profit off their own crimes, that's why Holler is able to keep all of the money he makes from  these items, even when killers send him items specifically to sell. eBay no longer allows Murderabilia to be sold on its site, and that's why most dealers have their own websites.

While Murderabilia is a controversial business, there are some victims who have benefited from certain sales. For example, Ted Kaczynski, the "Unabomber (sketch pictured above)," who's serving a life sentence for his infamous nearly 20-year bombing spree that killed three people and injured nearly two dozen others.

As ordered by a judge, nearly 60 items found in his Montana cabin were sold at auction, raising more than $200,000 [View  video of items auctioned]. All that money went to the Kaczynski's victims and their families.

While his typewriter, his infamous glasses and his hoodie were big sellers, the didn't even come close to the biggest ticket item. A set of 20 personal journals that revealed Kaczynski's thoughts and feelings, his life in the wilderness, even descriptions of some of his crimes, went for nearly $41,000. Those journals could be useful to investigators to identify future violent offenders and stop them before they commit deadly crimes.