As far as I know, Tokyo is one of or is the most expensive cities to live in, so I would it would be possible that the average salary there would need to be a little higher there for people to afford to live there.
The cost of living has to be considered.
Perhaps a worker in Tokyo does make something like $50,000 U.S. Though that may seem like good money to people living in the U.S., it may seem like only $25,000 for a person in Tokyo.