We've all made a really dumb purchase at least once. And when you're a young, world-class athlete, those dumb purchases can be quite expensive.

In a recent interview with Dallas Mavericks forward Harrison Barnes on The Players' Tribune, Emmitt Smith told the story of how he once spent $100,000 on a car as a 20-year-old. The ex-Cowboys running back recalls being insulted by a sales rep and spiting him by buying from a different dealership.

Here's what he had to say:

"I wanted to treat myself to a convertible Mercedes Benz, the SL. It was burgundy. Funny story, though. Before I actually bought the car, the car dealers treated me like I couldn't afford the car. I walked onto the lot and I was looking at brand new cars and the sales guy took one look at me -- a young African American guy -- and he walked me to the used car section. He said, 'Uh, let's try to get you into something that you can afford.' He didn't have a clue that I was on the Cowboys. So I looked at what he wanted me to look at, and then I said, 'No, I'll go with the SL. But I'm not gonna buy it from you.' And I went to another dealer and got it there."

In a 2016 interview with CNBC, Smith said the best financial advice he ever received was from Cowboys owner Jerry Jones.

As you might be able to guess, Jerry would not have advised buying that Mercedes.

"He taught me about finances with a simple statement," Smith told CNBC. "He always said, 'Have a big front door and a small back door. Take in as much as you can, and spend as little as you can.'"

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