One has to assume that there must be a market for clinically obese women or I wouldn't see so many of them polluting the pages of Adultwork. A prossie will always charge what she thinks she can get away with. Ultimately, if there are plenty of idiots out there willing to fork out £150 for a fatso, then why would she wish to charge any less? In her shoes, I certainly wouldn't!
The market dictates these things, so in this rare instance, I'm inclined to agree on your specific observation. It's horses for courses.
I decided not to punt this week, because I couldn't be bothered and had other stuff to do, but I had a lot of difficulty trying to find an escort who is size 6-8, or a small size 10. I also saw a lot of bullshit on adultwork, "size 8/10 with 38DD breasts" etc, I could be wrong but I don't think a size 8 woman can have a 38" back. With regards fat women if someone wants to pay £150, so be it, if she offers a great service and the man enjoys himself, fair enough. I think it was said by Jimmy that a long time ago, most WGs were thin, now most seem to be fat. The fact hardly any are below a size 10 is surprising and disappointing to me. The fact England has the fattest or most obese women in Europe is shameful, I think Romania and Italy are the two thinnest.
Don't get me wrong I have punted some fat women in the past, I've never paid more than £100 an hour and I do prefer thin girls, but I like variety and like I say certainly in Yorkshire if you don't want to punt a fatty or a granny, you're limited in your choice.
Writing BBW is probably easier than writing big, fat wobbly bottom, scale tipping biffers.