Not sure what these prices are based on, but in Tokyo a monthly pass for all of a zone doesn't even exist - you'd get a pass for a specific route from station A to station B only, with no buses and so on.
That's a good find, but note that the name is a bit misleading: "Tokyo Metro" is only one of many train/subway corporations in Tokyo, so the pass is far more restrictive than the London one. There are a few company-specific passes like this but they're rarely economical since you have to change company to get pretty much anywhere except on your own line.
