I’ve purchased hardcover fanfic before (Fallout Equestria). If anything, it supports fans and fandoms and makes them more likely to purchase from source. Is the estate really dumb enough to think this hurts their “potential revenue?” IP is a thing, yes, but as a fanfiction writer myself, derivative works can take a huge amount of effort and it’s a shame they rarely see financial rewards from it.
If they want to play the game, might as well do a few interesting challenges and earn some cool shit.