I'm a Neo Geo collector, but I'm certainly not rich.
Now, if you are talking about Neo Geo AES collectors, then yeah, those people are beyond rich. They're like, Saudi Prince rich. I don't think you can own a legitimate Neo Geo collection without also owning a few oil wells.
As for how I organize, depends on the system. It's mostly alphabetical, but I also like to keep uniformity in my spines, so like with my Genesis games I'll have all my black grid cases together, all my red strips cases together, etc.
I used to keep my Saturn games organized by genre, but now that I'm trying to go for a complete US set, I'm keeping them all in alphabetical order and region separated to make it easier to keep up with. It does hurt me a bit inside to have Ultimate Mortal Kombat 3 so far away from Mortal Kombat 2 and Mortal Kombat Trilogy, though.