It's still Income minus Expense, right? For a single founder, it's exactly as though the $25 book costs $1 to make, because you are the printing press, binder, paper supplier, ink supplier, distributor and author.
Yes, you can arbitrarily drop that number by having the business pay you a "salary". But the end result is the same. The money going out the door (to people other than you) is a tiny fraction of that going in.
The 90% figure refers to 'gross margins' and really means 'income minus cost of goods sold'.
In software, usually 'gross margins' are meaningless - it's a term used in most other industries and from classical economics wherein most of costs were actually COGS.
"Yes, you can arbitrarily drop that number by having the business pay you a "salary"."
No, it's not 'arbitrary' at all salaries and operating costs are the relevant costs to the business.
Software (and books) are IP businesses - the 'cost to make the book' or to 'run a website' are not useful in terms of understanding the business or profitability.
FYI - for most 'software businesses', net margins (i.e. after 'salaries and operating costs') are negative.
... so if salary is zero, gross margin and profit margin are the same. Which is the case for a single person business.
I understand the point you're trying to make, but it's still a bit silly to suggest that my business is not profitable because I may eventually spend some of the money it makes.
It's still Income minus Expense, right? For a single founder, it's exactly as though the $25 book costs $1 to make, because you are the printing press, binder, paper supplier, ink supplier, distributor and author.
Yes, you can arbitrarily drop that number by having the business pay you a "salary". But the end result is the same. The money going out the door (to people other than you) is a tiny fraction of that going in.