The surprisingly frugal habits of 8 billionaires

Frugality is a subjective term. To the average Joe it could mean eating meals at home or scouring the internet for cheap flights.

But to a billionaire it means showing up to work in a T-shirt and jeans, driving a Toyota or Volkswagen, and, in some instances, foregoing the purchase of a private jet or lavish vacation home.

Surprisingly, some of the richest people on earth are incredibly frugal, each one with their own penny-pinching habits.

From eating lunch in the office cafeteria with their employees to residing in homes worth a fraction of what they could afford, these eight self-made billionaires - many of whom are also generous philanthropists - know the secret to keeping their net worth high.

This is an update of an earlier version of this post.