MRIs are cheap in Japan because the Japanese government will only pay so much for them. As a result, there is less of an incentive for people to develop new imaging technologies since the government will similarly limit the profit that can be made from them. That doesn't mean that innovation in that field will stop, especially since more profit can still be made in other countries. The pace of innovation is just likely to be slower.
I didn't say incomes were rising. I said disposable incomes are rising. I can't find data to back that up, especially since the economic definition is different from the colloquial meaning of "disposable income." However, it's clear that technology has made both the necessities and luxuries of life far cheaper over time, which leaves more money for us to spend on other things even with a stagnant income.