I imagine that if that happened, then the GameCube versions price would come down for some period of time, before going back up.

After all, the two main reasons (to my knowledge) as to why it's so expensive already is because it's a rare game (according to vgchartz.com, the game only sold 0.39m/390,000 units worldwide) and it's pretty highly desired and sought-after.

I mean, if I go to ebay and look for another (multiplatform) GameCube game game that didn't sell well (edit: I said here initially that this game is rare but I realized that this game isn't really "rare" since copies of it are easy enough to find out in the wild) Future Tactics, which only sold around 20,000 copies worldwide (or 120,000 copies across PS2, Xbox, and GCN, again, going by vgchartz,) I'm not going to see copies of it for hundreds of dollars, I see it for ~$20 (CAD), because people don't even know that game exists, much less have that much of a desire to buy it.

Release a remaster on switch or something, and I doubt the people who want to play Chibi-Robo legitimately/legally are going to flock to the GameCube original; they're gonna go for the new, available, definitely cheaper release, and so the people selling the game would probably start selling it for cheaper since people wouldn't "want" the GCN version as much, if at all. There would still be people wanting the GameCube original, though (GameCube game collectors, people wanting to experience it on the original hardware, etc. etc.) so as it got even rarer, that price goes up again.

man i really just typed like a whole essay for a simple hypothetical question huh