A new documentary on legendary investor Warren Buffett sheds light on just how his spending habits may have made him wealthy. In the documentary “Becoming Warren Buffett,” which airs on HBO, the billionaire said he never spends more than $3.17 for breakfast most days. "I tell my wife, as I shave in the morning, I say, 'Either $2.61, $2.95 or $3.17.' And she puts that amount in the little cup by me here [in the car]," he explains in HBO's documentary "Becoming Warren Buffett," which first aired Monday. The 86-year-old, who is the third richest man in the world, usually gets his breakfasts at McDonald’s on his way to work. "When I'm not feeling quite so prosperous, I might go with the $2.61, which is two sausage patties, and then I put them together and pour myself a Coke," Buffett said in the documentary. "$3.17 is a bacon, egg and cheese biscuit, but the market's down this morning, so I'll pass up the $3.17 and go with the $2.95." The investing guru has long had a reputation for frugality, as he still lives in a 5-bedroom house in Omaha, Nebraska, which he bought for $31,000 in 1958.