SIDESHOW is just trying to scalp more their customer base.
Due the global economical crisis they know they will lose the "weak" slice of customers (these days there is less ans less people willing to spend 350/400 bucks for a Premium Format).
So they try to grab as much money they can with less customers.
A Legendary Scale has NOT 6 times the labor cost of a Premium format.
The polyresin is a VERY cheap material, it cost only few cents per kg. when bought wholesale.
the clothes are much bigger so much simpler to be produced.
Also the paint is easier to be applied.
Only that the sculptor is paid and the mold made,
the only cost is the cheap chinese (maybe child) labor.
Consider that for the same price in Europe you can buy a 1:1 Life Size statue with led lights
https://www.youtube.com/watch?v=1_ehpIZWkzU