I recently visited Japan, and brought with me all the breakfast foods I knew would be expensive in Japan. Pop-Tarts, children's cereal, grown-up cereal, Skippy peanut butter, bulk oatmeal, corn flakes. In Japan, they cost 3-4 times more than in the US, because non-rice staples (corn, wheat, oats) are imported, or grown in small batches. In the US, an ear of corn is 25 cents - 33 cents, in Japan, $2.00? The peanut butter in Japan is overly sweet and disgusting. I was surprised to find that cereals and Pop-Tarts are too expensive to mail to Japan, because they weigh so much. I tried to mail them ahead of my visit, but in the end, I had to take them in my suitcase.
Fruit is also exorbitantly expensive in Japan. I recently bought a round watermelon, about half the size of a typical American watermelon, and it cost close to $20. I think fruit in Japan is treated as a gourmet item, and grown with the loving care of Kobe beef. I think each budding fruit gets a serial number and personal attention, such as a plastic bag around it to protect against insects, with lots of culling to make sure that the ones that survive are the biggest. It's completely frustrating, because you can't buy an ordinary hand-sized apple. All fruit have to be perfect giant-sized specimens, meaning that an apple is so big, that you have to eat half and refrigerate what's left, ruining the second half. I asked a Japanese friend about this, and she said that no one would buy ordinary fruit off a tree.
Surprisingly, it's really cheap to eat out. If you eat out in the US, you never get a set meal, you have to buy the drink, the soup, the salad, the entree, all separately, and when you add in tax and tip, dinner out comes to at least $30. In Japan, green tea is basically like water and comes free, and most dinners are sets that include miso soup and rice (and trace quantities of salad). I think you can get a satisfying meal for around $15 on average. I also assume that second helpings of rice are free in many of the cheaper restaurants. Considering how expensive grocery shopping is in Japan, eating out seems like a good way to save money.
If you want to save on grocery bills in Japan, growing your own vegetables might be worth it.
Mari