The costing of the call depends on the value of the service provided by the call center. The international call centers will be driven by a globalization, increased competition, customer expectations and the fact that products are becoming more and more commoditized with improvement in computing and database management skills. It is not so easy to shift because of lower staff costs. Lower staff costs should be backed by a skill set which is language and cultural specific. The other things that impact operations of an international call center are real estate expenses and telecom expenses.
Call centers can be of different types.
A regional call center implies that a center in America to handle America, Europe to handle Europe and a center in South East Asia and Australia to handle Asia. This enables some economies of scale but duplication of efforts can minimize operational efficiency. The other option is to have a global call center where all calls across the globe are handled. This results in tremendous economies of scale, which is really cost effective. Such a center cannot afford any downtime because of lack of back up.