50th percentile + 30 years subsistence is not "fuck you" money, but regardless, income has multiple effects, not only cultural. They don't want to be financially supporting foreigners, of course.
30 years of money banked is quite a bit no matter which way you slice it.
It’s pretty much the definition of fuck you money
Having enough money to not lift a finger until the year 2056 is absolutely in the "fuck you" zone.
30 years of living expenses banked is absolutely "fuck you" money. 50th percentile income is not.
A rough calculation suggests the floor for '30 years subsistence' is about ¥120m/$800k, a sum that's pretty much impossible to accumulate at the 50th percentile of wages.