That and Graces is on the Wii, and TOS2 on the Wii didn't sell very well (Gee, I wonder why >_>).
It sold very well in Japan (not as much as a mothership Tales in a platform with actual userbase in Japan, but hey...) and nice in US, considering it sold as much as Vesperia did and it was a low budget game with recycled assets, plus the location process costed a lot less with ToSDotNW, it has to sell less to turn a profit for starters.
I'm sure Namco regards it as a success. Shame that doesn't change how half assed the game really was.