Cointerra is talking about a 500 GH chip. Are you really trying to claim that their chip uses $500 of silicon? Or even $400 worth? I don't think that silicon price is the limiting factor in any of this; I just looked up the price of silicon and unless I did something very wrong it looks to me like that amount of money would buy you like a KG. Additionally, many of the costs you are talking about (e.g. testing) are probably about the same regardless of number of chips on a board.
Until we see Cointerra's dimensions it is hard to say. As for looking up the price of silicon, make sure you are looking at the cost of a printed wafer. Blank wafers are used by FABs to print chips. Those 28nm FABs costs billions to build and have a limited economical lifespan. The price of raw silicon is pretty irrelevant.
Still I don't really care enough. If people want to wait for sub $1 per GH/s assembled miners well let them. I don't own any of these companies.