There really is no income that makes you comfortable because your definition of what is comfortable expands as your income increases.
If you make $40,000 maybe you live with a roommate, you phone has a cracked screen and it's three generations old, and you don't eat out at all.
When you make $75,000 you may rent your own place in the outer boroughs where you have to take a bus to the nearest subway station, treat yourself to a take out meal once or twice a month, and maybe go for a ski weekend at Hunter or Killington.
When you make $110,000 you get a place where you can walk to the train, take a week off to go to Cancun, and get the latest smartphone.
And so on, and so on.