—collecting all the boos changes your flashlight beam to project a boo face, and collecting all the gems makes the Poltergust's plunger diamond-encrusted. While both are neat visual flourishes, they're so minor that they ultimately feel pointless.
That's not a huge deal in and of itself, but so far in my playthrough (up to floor 6), the only things I can buy in Gadd's shop are:
1. Gold bones (giving you an extra life when your health reaches 0)
2. The ability to show a gem on the map for 1,000 gold
3. The ability to show a boo on the map for 1,000 gold
And that's it. So here are my questions:
1. Do any other items become available for purchase later on?
2. Is there some sort of NG+ mode so you can actually use the boo flashlight and diamond plunger during a playthrough?
3. Do the boo flashlight and diamond plunger carry over into multiplayer mode?
I have a sinking feeling that the answer to all three of those questions is "no." And if that's the case, the entire economy of the game is irrevocably screwed. The vast majority of your time spent exploring the nooks and crannies of the hotel yields you money, but if there are only three things you can spend money on, and all of them are that superficial (including the gold bones, as I've not come anywhere close to dying so far... and I'm guessing even if you do die, the penalty is quite minor), that means a thorough playthrough of sucking up everything you can and hunting for secrets is ultimately in service of nothing.
I'm getting flashbacks to New Super Mario Bros. 2 here, where collecting coins was such a huge part of the game, yet the reward for amassing a million (which the game presents as an overarching ultimate goal) nets you... an alternate title screen. At least 50% of my time in Luigi's Mansion 3 so far has been spent vacuuming everything I can, and knowing that it might all be a complete waste is seriously hampering my desire to do anything other than stay on the critical path.
There's obviously an argument to be made that the act of exploration and sucking up every little thing is a reward in and of itself. The animations are lush, the interactivity with the environments are top-notch, figuring out the puzzles to collect the gems is oftentimes delightful, and having a weapon that inhales mounds of cash to the effect of satisfying coin clinks and the rustling of dolla dolla bills y'all is music to my ears. But if the economy is ultimately as borked as it appears, that will assuredly knock my impression of this game down from masterpiece-tier to merely good—great. The idea of 50% or more of your playthrough being a complete waste in terms of progression or reward is so, so disappointing.
I hope to King Boo I'm wrong in my assessment.