You are making a pretty big leap by thinking that the car should be scrapped, you haven't seen rust until you have looked at a 10 year old car where road salt is used. Or a 15 year old dump truck that the frame rusted so bad it sagged in the middle.

Carefully remove the weatherstrip, wire brush the rusted area, apply a rust stop like Extend ( made by Permatex ) , apply white Rust-oleum, replace the weatherstripping.

Also, don't believe any of the "Book" value sites, they are wildly inaccurate for low volume cars and are often just a guess on their part. R129 SL values have been low for a while and I'd expect $ 6,000 to be average selling price not scrap value.