Based on a TV programme I was in Japan, I challenged myself to live on less than 10,000 yen (the psychological equivalent of 100USD or 100 Euros) over the course of one month. I spent 9,300 yen on food and things needed for survival (not including the apartment). I did not try the same experiment in China for health reasons – the absolute cheapest food would not provide me with all the nutrients needed. I estimate in China, the lowest I could have gone would have been around 50USD while still maintaining my health (if not sanity!).
Now that I am in South Korea, I have startup costs. Nonetheless, I got my mobile phone and other assorted one-off items before my first month of work began. In my wallet, I have 100,000 won. It is somewhat more than 100USD and somewhat less than 100 Euros. Being at training where food is provided, I have not used up any of that 100,000 won yet. I will likely be getting a "settlement allowance" next week, but with the magic number in my wallet, it is very tempting to try and see if I can live within that magical amount of money, and maintain both my health and sanity. So far, my impression is that Japan is cheaper than South Korea for food, particularly in the area I will be living.