They are more productive, in addition to being better paid.  Much of highly paid escort's renumeration is due to human capital improvements that make her time worth more than the street prostitute's services.  Same with doctors and other service sector work. The introduction of the concept of quality greatly complicates any model of the world which tries to connect physical resources with historical productivity measures.  It turns out that physical resource production and use are just proxy's for the unobservable concept of productivity. (This is similar to the way income is just a proxy wfor well being.) That's why measuring inflation in terms of consumer price indices is so problematic, for example.

You would measure productivity, in terms of service, by the number of people a service worker can serve. But it is entirely possible to measure it in the quality of service provided too. But since quality is a largely subjective concept, how do you really know what part of income increases are due to quality improvements and what part are due to productivity improvements in the non-service part of the economy?