Missing from the article that also plays a role:

* optimizations. Some of these restaurants don’t have a counter, or any customer facing staff. Select your meal and pay at a vending machine, get your ticket number, wait for your order to be called. * onsen/community center: it’s entirely feasible to own less things and have fewer sq/ft at home if you can go to your local rec center to shower/spa, watch tv, sit on the couch, eat dinner, hang out with friends, etc. as a tourist my meal+spa+etc was maybe $10? * public transit: a lot of these shops are viable in Tokyo because rails move people en masse quickly