Matt Kenseth had no idea attending a '70s-themed New Year's Eve party on Dale Earnhardt Jr.'s property would be so expensive.

Kenseth grew mutton chop sideburns and a fu manchu mustache as part of his outfit for the '70s bash, and it was greeted with much enthusiasm by host Earnhardt Jr. (who was dressed as Evel Knievel).

Earnhardt Jr. thought Kenseth's facial hair was far out and immediately began a campaign for Kenseth to keep it. He ultimately bet $2,500 that the Roush Fenway Racing driver couldn't keep his beard through this week's NASCAR test at Daytona International Speedway.

"He kept upping the money and upping the money until finally I said, 'OK,'" Kenseth said.

Kenseth double-checked his calendar to see if he had any preseason photo shoots lined up and thought he was in the clear. But he wasn't.

Roush Fenway's public relations department called him after the bet to tell him there was a photo shoot and interview on his calendar – which required him to shave.

"I guess I lost," Kenseth said.

But here's the kicker: Kenseth hasn't paid up yet, and Earnhardt Jr. told the NASCAR media he wants the money.

"Y'all can remind him that he owes me $2,500," a smiling Earnhardt Jr. said. "... We actually sent a few texts back and forth to confirm the bet – and he shaved his beard. You guys can remind him I told him to go to the bank, but maybe he forgot. I want my $2,500."

Kenseth responded by telling reporters, "I'll try to scrounge it up somewhere, I guess," but lamented the party host's sober-ish state.

"Back when he was younger, he would have had enough beers in him that he wouldn't have remembered that," Kenseth said.

(Photo via @matt_kenseth17 Twitter account)