Many years ago, this would have been in the late 1980's, something happened that I've never forgotten, and it bothers me to this day because it's one of those small cruelties that is a warning sign for society at large.
My ex- and I were vacationing, visiting Native American friends, in New Mexico. We decided to send a post card to his nephew who is developmentally disabled. We knew he'd love these special post cards where instead of a photograph, the "card" was a thin sheet of copper engraved with pretty scenes, animals and so forth. Pasted to the sheet of copper was piece of cardboard, which was like a normal postcard where you wrote the address and your message and placed the stamp.
Weeks later we were visiting and shown that the postcard had arrived without the copper. Someone had gone through the trouble to peel off around all four edges the copper, loosen it from the glue, and let the torn piece of cardboard continue on its way through the US mail. Imagine how the peeled off backing made it through the mail just fine and into the very hurt and baffled hands of our developmentally disabled nephew. While not a child in years at the time, it was still a crushing disappointment and one we could not remedy, obviously.
Worse is that he had not realized what he received (that it was marred and incomplete) so until his parents spoke up, he just wondered why we sent him a tatty ratty piece of cardboard from New Mexico.
This was way before the "expensive copper" syndrome; this was just mean.