Very true. That book (great btw) is also a bit of an uncommon circumstance. Hasn't Warren Buffet been saving since he was 12 and not spending a dime on anything? Does Zuckerberg drive a Prius? Yes.
Wealth is a funny thing, it is truly how one chooses to manage it. If watches are your thing, and you have no other interests or expenses, you could probably spend quite a lot on a nice timepiece. If you are into other things (obviously Apple products) you may want to make exceptions to your other spending. All in all, you deserve what fits your needs and what you can responsibly afford.
I will likely never own any watch of the B&M, Panerai, Patek, High-end Rolex fashion. Multiple reasons, I don't care for the style sometimes, I'd rather place my money somewhere else, etc. This isn't for any other reason than personal preference. At the end of the day if a Seiko makes you happy, then buy a Seiko. If someone has a problem with it, there are much larger issues at hand. *pun intended*