In Luigi's Mansion 3, there is an absolute ton of money to collect. Dollars, gold bars, coins, and more are scattered all over the place. There's nary a room in the game that isn't chock-full of cash to grab. The thing is, there's really not all that much you can do with the money! Why did Nintendo include so much moolah to collect, but not offer up much to spend it on? Nintendo's Kensuke Tanabe explained in an interview with Kotaku.
“The ‘feedback that acquiring money makes one feel happy’ is something that has been demonstrated in Super Mario and The Legend of Zelda, so it was something we wanted to include.”
The dev team also wanted to point out that the money in the hotel wasn't put there by the ghosts, but had been stashed away there a very long time ago. That's an intriguing little bit of detail, but Nintendo didn't share anymore insight into why it was stashed there to begin with.
Nintendo were inspired by Mario and Zelda history when adding money collecting into the Luigi's Mansion series, but that's not the only bit of nostalgia you'll find in Luigi's Mansion 3. The game pays tribute to the Virtual Boy with the Virtual Boo, a communication and map device in-game. The Virtual Boy wasn't exactly a hit for Nintendo, which might lead you to believe that there was some reluctance to add it into Luigi's Mansion 3. According to Nintendo's Yoshihito Ikebata, that wasn't the case at all.
“The impression with the Virtual Boy is that it’s a ‘machine that specializes in three-dimensional expression,’ and is a part of Nintendo history. Regarding putting this in the game, we had a good idea with the Virtual Boo name that was applied from the start. From within the development team, it was decided from the beginning of development to use that as the subject. There wasn’t a negative response from Nintendo internally, and it was approved without any problems. I believe that there are users who aren’t familiar with the Virtual Boy, but it would be great if they used this opportunity to learn about the Virtual Boy.”