They're out of their minds bidding 21K + on a car that lists for $10K USD in other parts of the world.

For one thing, I can probably buy a nice E320 CDI with the same buy-it-now pricing as this indidual has set on his listing.

For another MASS is what wins in ANY collision. Where does one think the energy goes after hitting a 4K lb object that was traveling at 50 mph? In the tiny Smart car, it goes nowhere but to the driver. The car bounces into the sky and lands on its side at times(according to footage). The passenger absorbs the brunt of the impact.
A car of its proportions can only absorb so much energy before the safety cage begins to collapse. After that, there are "complications".

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)