I have 2 fat bikes, one is steel and needs to be sold, the other is titanium and replaces the steel one for winter endurance races. I upgraded a few months ago after doing a 80 mile race in January on the steel moonlander, the new bike (used and actually older than the "old" bike) sheds about 15 lbs of weight which makes a huge difference for those races. (hoping to do 160 mile Tuscobia race next January)
I have a hardtail for mountain biking and mountain bike races. I also ride a lot in Colorado with a friend and it's very difficult on some of the trails with a hardtail. I would like to get a nice full suspension, but that bike will have to wait. But some day I will have two mountain bikes... :)
I have a road bike for training and just riding on the road with the local cycling groups. Just getting into that, helps keep me fit for the riding I actually love.
I have a "towny", which is just a heavy all purpose bike with panniers for getting to and from work, getting groceries, and just running around town.
So I have 5 bikes now, with 1 going out the door, but 5 is my ideal number if you add the eventual full suspension mountain bike. My kids each have a bike so that is 3 more for a total of 8 in the garage. Some hang from the ceiling when not in use or go to the basement where I have a shop.
The key is that each of my 5 bikes where purchased used, for less than half of retail. The titanium fat bike would have cost about 3 times the price if purchased new, and won't drop much if anything in that years ahead. The road bike is very nice and probably cost $3k new, but was purchased for $200 from my cousin last year, it's probably 10 years old. You can have a lot of bikes and be mustachian, and have just a couple bikes and be consumerist. The number of bikes means nothing.