So I didn't know about this game (I've never played Fire Emblem) and I just looked it up. I pay less in monthly rent than this single Gamecube game. I'm assuming there isn't a remaster or something and it's a gamecube game so it's not like there's a VC.

It's a used copy, the money isn't going to nintendo. You don't have to to play it of course but you can't expect people who do want to play it to pay that amount of money when it's going to some dude who is reselling instead of Nintendo.

If it was Nintendo asking for 400+ euros you might have a point, but it isn't. Both you and Nintendo are better off if you pirate the game, buy it when it's sold digitally and spend the rest of the money on brand new Nintendo games.