Toyko has about 2.5 times the population of New York city, which is why a "large" 225 sq ft studio apt goes for $1500 a month. (parking, management fees, and key fees are among the extra$ ).
If you can find a room mate (hopefully someone you don't mind sleeping VERY close to) you might get a deluxe 450Sq ft with a window for $2700 and up.
San Francisco (in the city) has half the density and San Jose/Cupertino/ mountain view are practically uninhabited wildlands.
You CAN"T compare major city densities in first world asia to anywhere in the US.
IE Hong Kong (I know, a broadband mecca) has 10 times the density of LA