That kind of gets back to what floats your personal boat. Folks have supercharged Nortons and put more than the cost of a Ductati into the job.
I think sometimes people just like to make what feels like a work of art to them, and by the way get that rewarding feeling of accomplishing something, that is hard to come by pushing paper or spreadsheets like many of us do.
Certainly owning old motorcycles is not going to pencil out as a money making activity for most of us. Our bikes have to be measured against
other more expensive hobbies to make any sense at all.
Do you need FCRs? Not really. Will some folks get a lot of enjoyment out of a well turned out Norton sporting FCRS? Sure.
You can do the job a lot cheaper but sometimes it is worth it to someone to have an excellent part to enjoy.
Let's match this up to a Porsche 911, a blonde LA mistress, or a Cessna 180. Cheap for the fun isn't it?
.. next question are they not overkill on a Norton?