So generally when I think of a neck-thru I think of this typical design

But on several high end basses I see a design more extensive such as this

So why the extra work on the neck? I mean by adding two extra layers underneath it what is really gained?

Also why so many layers in the body? I'm used to the typical top wood and body wood laminates, along with the top/body/back design with the top and back being the same, but on that bass it has 5 layers, and all I have to say is: Why???

Bass nerds / tonewood aficionado's help
The extra effort on the neck laminates is there primarily to blow people's minds when they see it. It works, too.

The multi-layer body compositions are mainly for the same reason. They're amazing and they add a bagful to the price. Some claim they have a profound effect on the tone, but this is debatable. You're talking about what is essentially a homogenous piece of wood. The varying densities will have some effect on string vibration, but how much is debatable.

That Ken Smith is gorgeous, though.
"Maybe this world is another planet's hell?" - Aldous Huxley
Because it looks awesome, and that kind of work going into the the neck and the contrast of the body layers just screams high quality and top craftsmanship.

Fodera does a nice job too:

Composite Aficionado

Spector and Markbass