I think most of the delusional sellers don't buy their MB's for the same reasons most of us do. Most of us enjoy driving and working on our cars and know that we will never recover anywhere near the money we have invested, and we are OK with that.
Those that think they are "investing" in their cars and are expecting to see a return when they sell are just setting themselves up for disappointment. It's hard to explain to them that when you buy a $500 car and put $2000 into it, you don't have a $2500 car, you simply have a $500 car that has consumed $2000 more than you paid for it-- it's still a $500 car.
Others may simply be victims of poor judgement and/or unscrupulous ebay sellers and are stuck with a car they grossly overpaid for and are desperately just trying to break even.