You're in fantasy land. I'm sure some make a lot, but there are many that don't.
Having been doing this for many years I agree with you - although I am going on my impression of things rather than actually knowing what they all earn. You can see a few who are very switched on and motivated to earn. They are running a business and act as such - typically they will retire at a time of their own choosing. I suspect they are earning big money.
They are few and far between. Some are simply seeing a few clients to earn extra cash - over the years I have found myself gravitating to this category, no deliberate strategy but when I look back that is what has happened.
The rest cover a wide range, as in most walks of life, and I think many are sitting around with no clients for long periods of time. I suspect the average earnings are modest.
I am not talking about parlours - no experience of them.
At the end of the day it is supply and demand. Whilst we individually might moan about paying say £140 or more per hour there are clearly many out there that do, otherwise prices would come down.