Then why flying business class if you care about that sort of cost? I've heard horror stories about economy class in USA, but I've flown 9h flights European-level economy and that's quite bearable (though not so pleasant) experience.

I was kind of thinking the same thing reading this and the above comment. I'm sure with a bit of saving I could afford a business class trip, but spending the money to spend extra time on vacation or doing something interesting seems to outweigh the thought of having some extra legroom or food.

If you're not a millionaire and pay business class from your own pockets, you're insane.

Most millionaires I know don't fly business class. People whose company is paying for their travel (and possibly are billing back a client), people using points, and the ultra-wealthy (>$5mm net worth) are the only people I know who would drop $10K on a 15 hour flight.