Speaking from experience of living away from home, I wouldn't recommend cooking Japanese food on a regular basis. It's very time-consuming as it focuses on delicacies and presentation. I rarely make my own sushi and I typically opt to go out to a Japanese restaurant so I can enjoy the eating and not endure the preparing. XD
Why not try simple Chinese stir-frys? You can eventually graduate to more complex Asian dishes such as curries/appetizers and you can even experiment with ingredients with your stir-fry (something you can't really do with Japanese). If you're pressured for time like me, I'll go for ready-made curries or sauces for cooking. South East Asia has a great variety of options to choose from. I still do this today....yum!
I would imagine making your own Japanese food to be expensive if you're making raw sashimi or something but.....miso soup? I don't know, my miso soup was quite easy and cheap. All I had to do was grab some miso soup paste, some seaweed and tofu.
Where do you shop? At your local Asian supermarket? I think the prices would be more reasonable there.