This is really weird - it looks like the people implementing the sales page code on https://verbum.com/advent-and-christmas that should make sure that owned resources are visible as such stopped including it after the first three or four books.
Okay, to some extent I was glad when I put the four or five most interesting things into my cart and found out the cart actually was empty since I owned all of them already. But then again, this is annoying. It is annoying because we know that the code exists and the sites can be much more helpful, it is annoying to have to raise this issue with every second sale going on, and in this case the site tricked me into believing the code was turned on.

Please fix this.