Back in the late '80s, early '90s, I came across an article in my local paper about the auction of a car hoard that had been sitting outside for decades. The owner had died, and his family decided to auction everything off. 1920s, '30s, '40s cars. The article quoted his daughter as saying people had approached him for years and years about buying individual cars. "$5,000.00," he'd say, even though the cars were rotting into the ground. Never sold any of 'em.
At the auction, entire cars were going for five, ten bucks each, because everything was rusted to hell after sitting out in the elements for decades. I could swear the article said some went for as little as $2.00. Buyers were looking at them and saying, "Maybe I can save that hood ornament." "I need those hubcaps."
Sometimes they don't even have to be in a field. I know of a '67 Pontiac Catalina 4-door that's been parked at a self-storage facility since at least 1985. First time I saw it, it looked pretty decent from the highway, apart from a low tire. Now most of the paint is gone, along with the wheel covers, and that low tire has been flat for years and years.