Outside London, and one or two other major cities in England I doubt whether there are all that many W.G.s pulling in £2,00 every week, added to which, of course, is that fact that unless the wheels have come off her menstrual cycle the average w.g. only works just over 3 weeks out of every four.
Bear in mind that W.G.s who do Incalls have the expense of maintaining a separate house or flat for business, with the attendant costs of rent, council tax, heating, lighting, etc. The more fastidious ones also spend a lot on clothes, toiletries etc just for business use.
W.G.s (once they start making a few quid) also tend to develop very expensive tastes in holidays (frequent), cars, and any other expenditure that doesn`t leave a paper trail for the Inland Revenue. I know one W.G. who manages to get through at least £40,000 - £50,000 a year with absolutely nothing but a full wardrobe, a houseful of expensive tat, and a DVD of holiday snaps to show for it, but she has a lot of holidays in the sun and gets through several cars every year.