Incomes are dramatically higher in the US than in Japan. Their economy has imploded so badly due to debt + currency destruction that they're now just barely above Lithuania (which has come a long ways of course) on economic output per capita.
Japan is no longer a primary economic power and their (perpetually falling) purchasing power + incomes represent that.
US GDP per capita is estimated at $92,000 for 2026. Norway is $96,000 for comparison. 340 million people vs one of the world's richest nations at 5 million people. The UK is $60k, and Japan is a mere $36k.
Read that again. US GDP per capita will soon be 3x that of Japan.
Doing a direct comparison of healthcare costs is silly accordingly. At a minimum you need to 2x to account for the drastically higher US incomes vs Japan, and at least 50% higher vs the UK.