There's a big difference between spending, say, $50 a day and spending $100 per day, in terms of how much money is needed to retire and how much you can save.

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.