This is largely a function of exchange rates. If you are paid in USD, then Japan will seem cheap in a way it does not for people paid in yen.

Vietnam is even cheaper.

The problem is you get paid in a roided up currency and it's a fun vacation for you. The locals get paid awful wages and a single night at an hotel for a typical person here is a whole month's rent for them.

Living there with local wages and taxes?

My British parents went there this year and found it very expensive

Not if you don't get paid very much?