The difference between someone with a high paying job who doesn't retire early, and one who does retire early, has nothing to do with eating out every night or buying coffee. That's the point.
A tech worker might make $200 a day after taxes. $5 on coffee isn't huge but in NYC etc it's pretty easy to blow $60 a day eating out and $100/day on rent, and that stuff can add up to where you hardly save anything.
For me, it's a question of values. I'd rather live frugally and have more freedom than trade away more of my time to have more stuff and convenience in my life. For others, the balance is different.