I can imagine that some popular agency girls can get an average of 4 punters a day, those who seem to get booked up pretty quickly. But I doubt that many independents who are arranging their own bookings are averaging 4 a day. That would mean they would need to be doing 8 a day to counter those days when they get no bookings.
I do think that most WGs are probably making very good money, but like footballers, their working timespan is usually fairly short. And generally, the more punters a day a WG sees, the shorter her working timespan.
And once they finish, what then? If they are wise, they salt the money away into property and other investments, or businesses, to secure their future. But you need a significant pot of money to achieve even a modest income (as anyone who has done any pension planning will know). However, for the majority, their expenses expand to match their incomings, and they walk away little or no better off than they started. If a girl is living the luxury lifestyle, then almost certainly she isn't saving anything for her future.
I am amazed at the amount of money that social influencers and the like can earn for doing nothing more than promoting themselves (at one time, someone who self-promoted was seen as a low-life, now it seems to be aspirational!). But I suspect that like footballers, there are very few earning the big money, and many, many who aspire to but will never actually make it.