In my experience one can generate about 15,000 words a month. And by a happy arithmetical coincidence, a month's living expenses when one isn't doing anything economically productive total about $1500. There you have it: a dime a word. Meaning a 100,000-word novel will set you back ten grand for the first draft, and probably another few thousand for the revisions. All things considered, that isn't too bad.
And the ratio might get better. I've been writing a hell of a lot the last few days; I have made the shocking discovery that it goes much more quickly when the subject matter isn't so damn serious all the time. At some point I got the idea from Iowa that prose could be sufficiently literary only if it was so dry and earnest that writing it became completely onerous. Well, to hell with the monastic self-flagellation. Right now I'm doing a scene on a volcano.