System.Web.Optimization bundle retrieving from cache cost a lot of time

Question

I faced a strange issue, while having the second load of the page, bundle must be retrieved from Cache, right? But what I see is that some long operations is performed on each request. Perhaps someone knows how to figure this out? Where does the figure of 250 ms comes from for the CSS bundle of 7kb?

Bundles are from default MVC 4 project.

The screens are below:

Answer 1

I finally found the reason. Actually MVC treats the bundle url as the real url and try to launch all the modules that specified in Web.config by default. Adding new config section

 <location path="~/Content/themes/base/css">
  <system.webServer>
    <handlers>
      <clear/>
    </handlers>
  </system.webServer>
 </location>

solved the problem and now additional time does not spend on each request.