This paper introduces an optimal cooperative caching policy for minimizing electronic content provisioning cost in Social Wireless Networks (SWNET). The SWNETs are typically formed by a collection of mobile devices, such as data enabled phones, net-books, electronic book readers etc., sharing common interests in electronic content, and physically gathering in settings such as University campuses, work places, malls, airports, train stations and other public places. Electronic object caching in such SWNETs are shown to be able to reduce the content provisioning cost which depends heavily on the service and pricing dependencies among various stakeholders including the content provider, the network service provider, and the end consumers. Drawing motivation from Amazon's Kindle electronic book delivery business, this paper develops practical network, service, and pricing models which are then used for creating two optimal caching strategies, namely Split Cache and Distributed Benefit for minimizing content provisioning costs in networks with homogenous and heterogeneous object demands. In addition to proving the optimality of the mechanisms, the paper constructs extensive analytical and simulation models for analyzing the proposed caching strategies and their optimal operating points.