IM SORRY HOW MUCH DOES IT COST???

One of the main reasons is nostalgia. As people who played games on the GameCube and the Wii in their formative years have grown up and began making their own disposable income, they look back on those days of their lives with fondness and rose-colored glasses, much like people around my age (I'm 41 myself) tend to be nostalgic for movies, video games and music from the 1980's and early 1990's. As such, many are willing to pay higher prices for such media they want to reexperience, often not knowing or understanding how pricing in certain second-hand markets work, and when resellers see the overall higher prices those people are willing to pay, they jack up the prices for everything even remotely associated with those markets in order to make more money for themselves, taking advantage of the ignorance of their general customer base. It's happened for generations, and not just with video games. Comic books, trading cards of all different kinds, vintage toys, and even vintage clothing all have been markets affected by this phenomenon over the last few decades.

On top of that, you also have just general scammers, gougers, people trying to otherwise take advantage of the overall economy's inflation, supply and demand, and sellers themselves often having complete ignorance of what it is they're selling that also can have sometimes big effects on second-hand markets. And while they usually don't directly affect second-hand markets and sellers, general importing and exporting agreements between nations can and is often used as an excuse by some as well to try and justify outrageous prices for certain items.

In the very end, though, anything on the second-hand market is only worth as much as people are willing to pay, so it's up to you, ultimately, and what you're willing to spend on something.