Pretty common. Rents get very cheap out in the suburbs. An apartment that would cost $2,000 a month in Roppongi might be $1,000 if twenty minutes outside the Yamanote and $500 if an hour outside. For many families, the only way to get affordable space is to get a house or apartment out in the sticks.

The other thing is that Japanese employers almost always pay for a commuter pass on top of the employee's salary, no matter how far away home happens to be. While people might not want a long commute at their own expense, it isn't a big deal when it is effectively "free" to the employee. It certainly helps to fuel the publishing and mobile phone industries here.