I ate an amazing lunch in a small Japanese restaurant in Zurich Wipkingen. Thought I'd recommend the place since it's a new discovery for me on account of it being away from the city centre and on a nondescript street.
I haven't been to many Japanese restaurants in Zurich, but I'd say it's on the cheaper side with excellent quality. I paid 23 CHF for my the lunchtime daily special, which included a soup starter and sashimi main with three types of fish.
I've been to that place! I lived in Japan for a while, and I can really confirm that this place is amazing, and fairly priced too! Here's a link to their website for anyone who's interested: http://www.samurai7.ch/samurai7/Samurai7-ENG.html