Other lines can be even cheaper, if you're looking for a minimal studio you can live within 10 mins of a major central station for < $600/mo especially if you choose less popular lines like Seibu Shinjuku/Ikebukuro line. $2k-$3k is already living quite nicely for many Japanese people, my mother in law lives in a 3 bedroom apartment for ~$1,000/mo in exchange for being ~20 mins away from Ikebukuro by train in a sleeper suburb.