Earlier quoted context omitted.
This is not meant to be a dig but just an observation for you to think about. Your last two comments are about how it isn't or shouldn't be possible to make money. It's true that market opportunities are hard to find, but you'll never find one if all you see is the "yes, buts". You miss 100% of the shots you don't take.
No offense taken. I'm just trying to have a healthy optimism about writing, marketing and selling a book. 500k and 120k in sales seems like outliers. Would just be great to hear more about those experiences though.
Search for the things that no one else sees or has the vision or boldness to turn into an outlandish success.
Take a chance. Live a little. Dig deep down for your inner crazy.