The question I am asking concerns publishing and not mathematics in a strict sense, the argument might be off-topic for this site... but I will try anyway.

Suppose that you are writing a textbook in advanced mathematics, say a book for mature undergraduates or graduate students. Suppose that:

You write everything using Creative commons, possibly in its most liberal version, which allows people to copy and rewrite your text, and maybe even to use it for commercial purposes!

As a consequence of the CC license, your text will certainly be freely available on the web. Nevertheless, you want to publish the book at some reasonable price, say 20$. You presume that a student is willing to pay a reasonable price for a hard copy even if it is freely available on the net.

What would you do? Is there any standard publisher in the mathematical community who would publish your book?

Further on, you might also realise that you are doing all the job (writing and formatting), and that you actually don't really need a publisher at all ... would you consider self-publishing?