Re: People will definitely pay for music.
Actually, that's the question. If we assume your statement
I think the answer is that Spotify is too cheap. But maybe that's all the cash consumers are willing to part with for it as a service?
is true, then no, people will not definitely pay for music, at least not at a level that supports the production of more music as a living.
It is true that some people will pay for music. In fact it is probably true that some people will pay a LOT for music. And we can see even here in the comments section at El Reg that some people will NEVER pay for music. The question then becomes can you achieve a mix of sales across those various groups such that some people will produce music to make money? Right now that is a very open question.