Elites (from the DLC) seem to be hardcoded to use silicon instead of having their choice like the tooltip says. Im on a mission where I have all the steel, aluminum and glass I need to upgrade, plus aluminum is much cheaper than silicon, and I still cant upgrade. 

Is there a way to switch it or something? I'm pretty sure this is a bug. You don't have to switch for something like the cold fusion patent; it just works automatically. I would think this would be the same.

I can upload a savegame file if you want to see it yourself. It should be pretty easy to reproduce though: just play as elite and deliberately crash the price of aluminum.