This does not show there is demand at a level worth making more carts. Rare items on ebay increase in price, but there are only a small amount available. It is low supply, that is driving the price.
Why anyone would pay more for a used copy over digital one is beyond me. Maybe they figure it is cheaper to buy high then resell high. Or maybe the listings sit on ebay for ages until some moron buys it.
As a physical collector I love stuff like this. My Xenoblade 2 CE alone is probably worth more than my entire 100+ Xbox 360 collection. Makes it feel like it's actually worth collecting.
I also don't understand the drama. People who wanted it have had almost 4 years to buy it, and if they want it now, they can just buy digitally. In the 90's you were just shit out of luck once a game was sold out. Contrary to populair believe on this forum, print reruns were pretty rare back then as well, for anything that wasn't Mario, Pokémon, Final Fantasy or other populair stuff.