Likely. A single machined mold for a plastic sprue in a modern HIPS machine is going to run five figures, let alone the cost of the machinery itself in the first place. Plastics are ****** expensive to setup even if the line to support isn't 400+ unique models.
Even assuming something like 4-5 mechs in the same sprue to save space and mold costs you're still looking at seven figures, minimum, to have the setup complete.
BattleTech isn't worth that to IWM, and it's vanishingly unlikely to ever even come close.