Toolian, I have been reasonable and explained why your analogy of 1890s plastics and action figure/toy/whatever plastics is flawed. You're talking about toys that are made in different propotions, with different quality levels, with different volumes of expected sales. You're even talking about a solid piece of HIP, which has nothing to do with a miniature, which is most certainly not a solid piece, with turrets and other things sticking out.
Let's see here.
The polystyrene used has been stated before to be the same as the material used in Catalyst's superb new Loki and Thor battlemech sculpts. The proportions of HML Leviathan have been shown and the detail level shown in the lucite prototype. I happen to know, as someone who has worked extensively with polystyrene miniatures, the properties of the substance in practical use in miniatures. I own several battlefleet gothic spaceships made of the stuff, and thinner does compromise it. loose wingtips and antennae are easy to damage, even when made to 3/16th inch thickness or thicker.
If any hollowness is involved, it's going to be to make an easier to produce sprue. A few forms of HI Polystyrene as a material is something around $1000-1400 per metric TONNE. Saving 50 grams worth in a battleship mini is not going to make a notable difference in miniatures cost. I don't know the exact cost of the type CGL plans to use for their minis, but I can't imagine the price deviating much from that estimate.
I'm pleased that you have worked in a plastics factory. I could tell you very much that I am an engineer. Does that change anything? What matters is how the material actually works. The difference in our arguments is that you assume somehow that those examples apply, while I am stating explicitly what we know so far related to this actual miniature, and polystyrene use in miniatures in general.