Calculations based on so and so much an hour multiplied up to vast assumed sums per annum, are very misleading. a solicitor/ accountant, medical consultant and so on, might charge £200 an hour but don't assume that means every hour is a fee at that rate, all day every day, others the same.
Those in prostitution that have set it up as a business and work full time at it will be making very good money but the better organised they are there will be costs - premises, consumables, kit, outfits, advertising, (not professional insurance in the case of hookers) but prostitution unlike the others mentioned, is largely cash based, which is less easy to launder once the sums get large and continuous, unless it is paid in and declared or a more organised system is in place.
Fact is that any type of work isn't likely to generate properly high life changing income unless they work pretty well full time at it and are properly organised with a business like set up, otherwise - the rest - the bursts of cash will soon disburse and the worker wont be getting rich out of it in a way that really alters or improves their riches over a long term.
So (aside from those with expensive addictions or big debts), some do it as a business and some do it to put some icing n the cake.
FF