This is how I got this achievement not 5 minutes ago:
The Phantom Corsair is worth 24,000 and the Deusenberg Walker Coupe is worth 25,000. Just destroy both of these, finish the case and you'll have it. They're both hidden cars, so their locations will be on the map.
Then again, you could just destroy a bunch of hidden cars and unlock the achievement, but those two cars are the only ones with values posted on the Social Club Website.