Notice one of the comments about those cars on the BAT site:
"This Mustang collection has been talked about locally for years (I live in Puerto Rico). It is said to have belonged to a well-off doctor who expected these cars to increase in value, as they did. Unfortunately, he did not take any measures to prevent rust, which, due to the proximity of the cars to the ocean, has probably rendered a good amount of them worthless."
If that doctor didn't think exposure to the elements would cause problems to his cars ... wonder how his patients are (were?) doing ....
T.