soy (in the form of edamame, tofu, and natto) is probably the cheapest option. Eggs are usually next on the list for people over here.
Edit: seafood might or might not be an option before eggs depending upon where one lives. Organ meat as well as we eat heart, liver, etc. a lot here as well.



If you have to take a train to the grocery, that’s a failure in local planning and a business opportunity. That said, not every store has everything and I, too, have taken a train to the grocery store for fancier/rarer things.
In some parts of rural Japan, we also have a grocery truck carrying staples and things you requested the last time they came from the actual store. This is a huge lifeline to some rural elderly people, but I don’t see why it couldn’t be more broadly applied in other areas.