Proxy caches have been used for a very long time to enhance the performance of web access. Along with the recent development of CDN (Content Distribution Network), the web proxy caching has also been adopted in many main techniques. This paper presents a new viewpoint on the possible improvement to the cooperative proxy caching, which can reduce outbound traffic and therefore ideally result in better response time. We take notice to the regional total cost of cache objects for optimizing content distribution. By contrast to the regular removal policies based on single proxy server, we prefer to evaluate a retrieved web object based on the metrics gathered from multiply proxy caches regionally. We particularly introduce a concept called post-removal analysis, which is used in measuring the value of the removed objects. Finally, we use the real proxy cache Squid to implement our proposal and modify the well-known cache benchmarking tool Web Polygraph to test this cooperative prototype. The test results prove that the proposed scheme can bring noticeable improvement on the performance of proxy caching.