The game is free to play, so the the majority of its "purchases" will be via download, and thus not represented in weekly sales chart.
The physical, deluxe starter pack has sold just over 70k in the last 2 weeks. What do we think the over download number is? 200k/300k?
source: http://n4g.com/news/1208487/phantasy-star-online-2-tops-350-000-users-in-japan-on-psvita-in-just-10-days