Marx explained how capitalism exploits the workers through lack of regulation.
There is, to my knowledge, no similar work on the theories of prostitution for no profit or promise of gain...
Perhaps I finally have the title for my retirement treatise..?
There is a crucial difference between interns and co-pilots:
Interns are of limited value; they fill some small gaps, but the positions are all about gaining experience, networking, and finding a career path. Interns will make up at most around 5% of the workforce in the organisations they serve, and when paid, are paid a very small amount, but probably a reasonable or significant proportion of that which might be paid to longer-term employees doing similar work. Internship has parallels with post-graduate qualification.
Co-pilots, conversely, are necessary to the operation of the aircraft; typically forming perhaps 40-45% of the pilot workforce, feeding expansion and providing a means of addressing attrition
There is considerable economic risk in replacing a significant number of co-pilots with pay-to-fly prostitutes. There is less risk in having a small number, and there is probably some profit if the deals are done well.