It's very hard to give 'average' costs. I live at the edge of Sapporo. If I moved downtown a few subway stops, my rent would go up 40%. If I moved a 30 minute walk away from downtown, it would go down as much.
Compared to what Avivet wrote, I have three rooms and a double garage for 60,000 per month. Japanese cities (except the biggest ones) have generally pretty low rents compared to Western countries because the prices have barely gone up in 20 years, while many Western city rents have consistently gone up.