I think the idea here isn't the absolute numbers, but that if Elon manages to successfully fleece everyone's retirement, it will collapse confidence in the market, which could wipe out far more value than SpaceX alone.

IF SpaceX is actually worth 400-500bn and it's a few hundred billion dollars of fleece, sure, that's a "small" amount (still.. lord almighty it is never enough for these people). But the hazard is that it is a fleece. That would shake confidence in the system, the bear case is basically unlimited at that point.