Expensive mics don't sound better, but they kind of 'flatter' certain sound sources)....
Well....that kinda argues in favor of them, doesn't it?
Sure, every car with 4 wheels and an engine will usually get you from point A to B....but would you really rather do it in a Fiat Panda or a Range Rover, and tell my honestly that you wouldn't be able to tell the quality differences between the two vehicles.
Don't get me wrong, I use a cheap
Cascade Fat Head or an old AKG D1000E basic/cheap dynamic for a lot of my guitar/cab recordings.....but when I do other things, I break out the more expensive mics, because they simply sound better for critical recording.
This notion that we never ever need anything that would be considered "expensive" or "high-end" when recording, is a silly notion, often pushed entirely on home rec forums, where budgets are everything.
The real answers is that if your going to do a lot of serious recordings with a lot of variety, you need a variety of gear, and that can be both inexpensive and expensive gear, low-end and high-end stuff.
In a typical pro recording setting, you're not going to get by with 2-3 $100 mics and a $100 interface, or whatever.