Microsoft Services Provider License Agreement (SPLA) is a licensing program that enables service providers and ISVs with a hosted offering to license Microsoft products on a monthly basis to provide services and hosted applications to their end customers which will reflect on your TCO for hosting , outsourcing and project cost for development as you will pay only number of seats for the total man days without any extra cost and you will be able to provide Microsoft license for your end users (Software as a Service) and benefit from the reduced license cost only for service providers.