Head to Ginza.
Ginza is where lots of high-end luxury restaurants gather, but some restaurants provide lunch at affordable prices.
For example, sushi. Ginza Iwa offers lunch sushi from ¥4,500 ~.
Or teppanyaki. ahill offers lunch course from ¥2,000.
You will be able to find the most delicious dish in Tokyo at an affordable price if you head to Ginza for lunch.