It is worth bearing in mind that earnings will keep accumulating for each title. You don't get paid only the once, but over and over again during the YEARS the book is likely to be for sale for.
Also, I'm a writer (actual books), not just a freelancer for DMG, and I can tell you that in publishing, thinking things like "min wage" is not the way to go
Book royalties accumulate in drips and drabs. Why do you think that writers are often depicted as impoverished, living in garrets
(or why many mangaka admit to living in small, rather old (and cheap)apartments)? Anyways, earnings wise, one has to take the long view, when working for royalties. I'm still earning for a book I wrote almost SEVEN years ago. Drips, drabs, and trickles, all adding up to income, from everything I ever published for sale.
As for TOWFL, I understood it to be copies...800 copies, not $. Though I am somewhat uncomfortable with people eyeballing my particular stats on their lonesome...it feels like someone's peeking somewhere private
and I think since not all titles will be as popular as others, we'd get a much better idea overall if we were given total number of all DMG books sold . Anyways, I'm not in this for the money but I know some are. If you are, you need to refine it so that you can do the work at speed, and take on more projects, clients etc. so that you can earn what you need at what the market actually offers. Or realise this may be an income supplementation rather than a career. Just sayin'