Most people have a pretty decent idea of how much grocery staples cost, since for regular people, it's a frequent challenge to fill up your cart while keeping your budget in mind. But when you're one of the richest people on the planet, you might not realize how much it actually costs to fill your pantry.

When Bill Gates visited The Ellen Show, host Ellen DeGeneres gave him the Price Is Right treatment, having him guess the prices of grocery store items. (Cleverly, the game was called "Bill's Grocery Bills.") He admitted the last time he had been to a supermarket was "a long time ago," and it showed.

Gates started out by overestimating the prices by a ton. He thought Rice-a-Roni cost $5, when it really cost $1. On other items, he got the price way too low. He thought a container of Tide Pods cost $4, when really it cost $19.97, and he thought a bag of Totino's Pizza Rolls cost a whopping $22 when they really cost $8.98. But on one item, at least, he was spot on, guessing dental floss cost around $4. (At least his dentist can be proud.)

With a ton of help from the audience and from Ellen, Gates got enough questions right to give the audience a prize: the chance to come back for one of her big giveaway episodes. But Gates didn't win enough for Ellen to pay off his kids' college tuition, a prize she had jokingly offered to him. Let's just say that won't be a problem for his family.

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