Namco confirms that Microsoft paid for the honor
Tales of Vesperia will continue to be an Xbox 360 exclusive in the same way that Heavy Rain is a PlayStation 3 exclusive, according Namco Bandai community manager Charlotte Toci’s post on Facebook. Why is this so? Microsoft paid Namco Bandai for the honor of the title being a Western exclusive for the Xbox 360 platform. (Still, we hear that the situation with Heavy Rain is different because Sony was the publisher of the title when it was released.)
Later, when the exclusivity period ended for Microsoft, a PS3 version was released. It took over a year, however, for Microsoft’s exclusivity to the title to end; and by then, most PS3 owners were interested in other titles.
It is thought that Microsoft helped fund the localization of the title in the same way Nintendo had paid for the localization of Tales of Symphonia. It is pretty safe to assume that this is the way that it works these days, and how companies secure exclusives. However, this trend seems to be that most publishers want to have or need to have the multiplatform sales, as many companies need to generate the revenue to recoup development costs.