This has been discussed often, some web sites keep cost statistics.

For example, Google: living costs london cluj

(I was outsourced to Cluj, Transylvania in Romania. I recommend it. 250 Euro/month for a nice, central 50 m2 apartment. People are nice, it is safe. Different. Beautiful women. Mountains, but no sea. University city. The food is very good, but could be more international -- a few sushi places and one(!) Indian. If you want more info, add a comment and your email in your profile.)

If I had a choice personally, I'd go for Japan. For culture/food.