Chinese food is more Americanized, therefore, more normal, inexpensive, very common foods can be used.
Japanese food uses more "specialty" ingredients- such as miso, seaweed, udon (noodles can be found here, but udon isn't the same as other noodles..).
Another thing to think of is the ingredients. I guess this ties into the more americanized food, but Chinese food uses less expensive ingredients. Japanese restaurants usually use expensive raw fish, highly trained sushi chefs, ect. It's more expensive.
That's bcz you have not go to the expensive Chinese resteraunt. There do are many expensive ones in the world.
I definitely agree with lookng at the ingredients. Chinese uses a lot of noodle and rice, Japanese uses miso and seaweed and plenty of fish etc, amongst other things.
two words: cheap labor.
Japanese is more expensive because the food (usually Sushi) requires more expensive materials.
Take for example. Fatty Tuna which cost about 200 dollars for 3 lbs.
Look at the ingredients. That's usually a key feature.