I'm trying to envision the pitch to, for example, Fromsoftware, makers of Elden Ring. Ignore the cross-game component for a second because that's mind-bogglingly dumb.
"You could have artificial scarcity of Rivers of Blood*! Imagine that only 1000 people could own it, and could auction it off, and you'd make a percentage of every single transaction! You'd have a brand new monetary stream in-game!"
Alright. Now try to wrap your head around a scenario in which, for a primarily single-player game, people wouldn't completely excoriate Fromsoftware for doing that. It breaks the story. It breaks the sense of achievement in-game. It breaks even the loose sense of community that the game has. It breaks the fundamental nature of the game itself, which is "you have the freedom to build your character how you want as long as you git gud**".
I just don't see the value added at all. There's zero point to it. There used to be games that allowed you to import your characters from older games in the series, for example Ultima. That was interesting for a minute as a bit of a novelty, but that quickly died off because it turns out that people really just want to start out at zero and work their way up. The idea of paying for it is just wildly crazy.
* note to reader: massively overpowered weapon that you get later in the game which takes your character to a completely other level.
** learn the game mechanics, enemies, strengths/weaknesses of weapons, armor, etc. An artificially scarce weapon would never get used.