Pure "Bigger is better"?

Besides the obvious over designed, some parts (like jaws) have no real use regarding mechanical integrity except as consumables (and allowing the use of a harder/softer material). That overdesign is pointless.

On the other hand:

• vices are old enough to be at a stable design regarding normal uses
• his stress tests (I didn't go through all) and focus on opening are pointless as if these are real criteria people just buy a leg vice which is designed for bigger items and stresses
• his stress tests focus on direct limit, where I'd guess fatigue has a word to say in failure

As for the 50% markdown (cost per mass is an ok approach): probably corresponds to the distribution + retail overheads included in MSRP which don't apply to online sales.