The comment thread is interesting. My response was:
This one's interesting for me, because while I aspire to a high degree of openness in my blogging about my writing life, I've never talked money, except perhaps in the most general terms. I'm very wary of doing so, I think because I've worked in business all my adult life (marketing, software and telecomm) and keeping financial info confidential is second nature to me, reinforced by the umpteen NDAs I've signed over the years.
I will go so far as to say I made about $15,000 off writing last year, which is a small but respectable fraction of John's income. It's by no means a living wage. I would be terribly loathe to break that out by source for anyone but my agent or the IRS.
*However*, I am the sole wage earner and provider of benefits for two adults and a child. Even if I were making well into six figures off books (!) I couldn't afford not to have a day job, because both the Child and her mother have chronic health conditions which pretty much mandate that they receive insurance through non-qualifying (ie, employer sponsored) groups. I'd have to make enough money to be confident of being able to pay $2,000-3,000 per month in free market health insurance costs for *years to come* before I'd begin to consider writing full time.
Ain't gonna happen.