Look at what goes into this chef's $5,000 burger 8:37 AM ET Tue, 21 Feb 2017 | 00:50

﻿Before I took my first bite of the FleurBurger 5000, I was one of those people who thought paying $5,000 for a hamburger was both obscene and insane.

After all, a top-of-the-line burger from Shake Shack or In-N-Out costs less than $10 — and they don't get much better than that.

But then I found myself in the kitchen of Fleur, Chef Hubert Keller's restaurant at the Mandalay Bay in Las Vegas. I watched Keller quickly sear a patty of Wagyu beef ($100 a pound) and douse it over and over again with rich butter, sealing in the flavor and the juice.

Then I watched him slice and sear a few slabs of prime foie gras ($45 a pound), and combine the duck fat with more butter to sautee a mound of sliced black truffles ($1,500 a pound). After that, Keller carefully layered the three ingredients onto a freshly baked brioche bun.