It’s the cabinet. They use excellent drivers but the cabinet makes a massive difference. By having such a well damped cabinet, they deliver an amazing sound. The molds for those cabinets are pricey which is why Wilson’s are soo expensive.
Yep.
I've had plenty of chances of hearing speakers in baltic birch or MDF, used for getting the design nailed down, then the same speaker in a CLD cabinet of the same dimensions. No other differences in the speakers.
The improvements are not trivial.
Lucky for the DIY community, there are some very effective, and not to difficult to deploy, constrained layer damping solutions. Maybe not up to what the high end manufacturers are using, such as Wilson or Von Schweikert, but much better than plain MDF of birch ply.