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Automakers regularly auction off noteworthy vehicles and donate the proceeds to charity. While that tends to happen with the first vehicle in a production run, Dodge is doing it with two very special end-of-run models.

The final Dodge Demon off the line will be sent to Barrett-Jackson's Northeast auction. That's not all, though -- it's being auctioned off alongside the final Dodge Viper. The two will be sold as a pair, sporting the same Viper Red paint on each body, and 100 percent of the proceeds will go to the United Way.

Dodge calls it "The Ultimate Last Chance," which seems fitting. While it's unclear what the future holds for the Challenger and its many variants, odds are the Demon was a once-in-a-lifetime sort of vehicle, given that it rides a fine line between a street-legal car and a purpose-built drag dominator. And Dodge has made it clear that the Viper has finally reached the end of the line -- heck, the automaker's even closing the factory where it was built, repurposing it as storage for historical vehicles.

If you're wondering how much one might have to spend for this pair, I hope you brought a few commas. The first 707-horsepower Hellcat off the line raised $1.65 million at auction in 2014, and they've built a ton of 'em since then. The Viper and Demon are both more exclusive, so it'll probably take some serious liquidity to win this auction. The auction kicks off on June 20, so you don't have much time to check under your mattress for a spare million or two -- or three, or four...