It's quite simple - high price low volume or low price and high volume. Phase One as a company is stuck in their low volume model, but CMOS is making it easier to design backs with broader functionality making them more attractive for a wider audience. Tech cam with live view, a huge opportunity in the landscape amateur market. There's still some technical challenges left, but I don't think Phase One pricing is a law of nature, and I think Mf future looks bright, from a photographer's perspective.
I don't think the 645z will be the last time we say "game changer". We'll see more exciting products over the next few years, and I think some will have reasonable pricing.