a. By train (that's why a Japan Rail Pass is the best solution)
b. By taxi: with the exception of short trips, taxis are expensive.
Please note that fruit and vegetables in supermarkets are also significantly more expensive in Japan.
For meals and accommodation, there are some interesting options. You can find tasty lunches for €7-8, even in Tokyo. For accommodation, Japan Experience offers traditional accommodation in the major tourist cities of Japan, with good value for money.
In short, it is entirely possible to quickly reduce the price of a trip to Japan by adjusting your various budgets (food, accommodation, transport), without sacrificing the quality of your stay!
Finally, we advise you to go to Japan with Yen (¥) from our partner Comptoir Change Opera (https://www.ccopera.com/). The vast majority of payments in Japan are still made in cash.