This article, originally published at 6:20 a.m. on Tuesday, March 22, 2016, has been updated with details of EBay auctions.

Under Armour (UA) - Get Report  likely could smell what Dwayne "The Rock" Johnson was cooking: the potential to make a ton of money together. 

The World Wrestling Entertainment (WWE) - Get Report legend turned Hollywood star told his 46.7 million Instagram followers on Monday that the first item in his partnership with Under Armour -- a gym bag -- has been met with ferocious demand. "100% SOLD OUT -- bags are now an instant collectors item," said Johnson.  He also teased upcoming product launches -- "Coming soon will be THE training shoe of all training shoes, training gear, lifestyle gear and some very cool technology."

The Rock began promoting his new line of backpacks about two weeks ago on Instagram, including a link to purchase them on his profile.

Hewasn't kidding about the bags gaining collectible status: Several well-bid auctions are under way on EBay for the backpack, with offers from $120 to $610. 

The Rock's Under Armour backpack is selling for more than $600 on EBay.

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Serious interest in a gym bag likely gives Under Armour confidence in the return potential of its most recent celeb signing. The actor and Under Armour inked a long-term marketing deal in January under which the apparel maker will design products including footwear, apparel and accessories inspired by Johnson's current films.

The first product was the Rock-inspired backpack and duffle bag introduced on Under Armour's Web site Monday, available in some of the brand's stores in the next few weeks.

Johnson joins a suite of athletes signed by Under Armour that includes Golden State Warriors guard Stephen Curry, No. 1-ranked golfer Jordan Spieth and Carolina Panthers quarterback Cam Newton.

An Under Armour spokeswoman did not immediately respond to a request for comment.