I have been thinking that it has to be the clean, freshly made fiat dollars, but then again I don't know... In my country, professors are paid by the government and that's pretty much all you need to know.
I am paid by the taxpayers of the State of São Paulo, to be more precise.You are payed by those who buy the bitcoins that you sell. That of course determines the opinion that you pretend to have about its future.