The diecast in iron man figures is zinc alloy, which is technically pot metal. Zinc is cheap to die-cast compared to other metals. Diecast is generally poor quality metal. So cheap pot metal, while coming across as a bit insulting considering how much we spend on these, is technically correct. What makes the diecast figures more expensive is not the cost of the material itself, but the cost of the tools/casting equipment to make them, which requires a much higher initial capital investment than making plastic pieces.
Given that you cannot see the difference between how equal quality paint looks on plastic vs diecast (just look at your "diecast" iron man and see if you can tell what parts are plastic vs diecast just by looking at them) - I would have personally preferred all plastic figures due to lower cost and additional pose-ability. However, I collect a lot of Iron Man's and rarely handle the figures, so the added weight which gives you a sense of higher quality doesn't really do anything for me. For those who collect fewer pieces, that added sense of quality may be worth it. I personally would prefer to save money to spend on more figures, but we don't really have a choice on that so no sense arguing about it.
