A $3 coffee everyday adds up to about $90 a month, when you can usually just drink free coffee from your office or buy some cheap pre-ground stuff.
Spending $5-6 for lunch each day at work can easily add up to another $100+ dollars a month, when you could just make a bunch of peanut butter and jelly sandwiches and spend a fraction of that.
So there's close to $200 a month, right there.
If you're trying to retire early, it's definitely way tougher on a lower salary. But improving your spending habits is an important skill for everyone, especially for those making less.