2 weeks => 8 work hrs. per day. 5000$:80hrs. = 62,50$
1 $ = 0,7592$ = 47,4479€ = 47,45€ ---------------- total: 3796€ in two weeks.
50€ per hr. is a german student designer/programmer (first uni year) price. nothing special. the most work for 70-120,00€ p. hour.
2) A book establishes a customer base, and Pete can provide future offerings to this pool.
3) A book is a great way to establish credibility in a space. When someone is looking to hire a consultant to work out Rails <> Stripe, who looks more attractive: the guy who wrote the book on it, or "generic Rails developer"?
The focus is on long term asset building, not short term gain.
I've definitely doubts about that price for a german first semester student. As a student in first semester you'll be a non payed trainee in germany.
I was interpreting the post as a statement of the average market rate, which is something else entirely.
A lot of technical books (for that matter: most books, regardless of subject) never generate a living wage from the book itself.
IMHO you are not factoring in the value of the built email list building. This will (hopefully) allow Pete to be exponentially more successful with future books.