Is it right that ASP.NET bundles get generated on every request?

Question

We hit a performance issue recently that highlighted something that I need to confirm.

When you include a bundle like this:

@Scripts.Render("~/jquery)

This appears to be running through (identified using dotTrace, and seen it running through this):

Microsoft.Ajax.Utilities.MinifyJavascript()

for every single request to both the page that has the include, and also the call to the script itself.

I appreciate that in a real world scenario, there will only be 1 hit to the script as the client will cache it. however, it seems inefficient to say the least.

The question is, is this expected behavior, as if it isn't, I'd like to fix it (so any suggestions), but if it is, we can pre-minify the scripts.

UPDATE

So, even if I change the compilation mode to debug, it's still firing the minify method. It outputs the individual urls, but still trys to minify it.

However, if remove all the references to the render methods, it doesn't try to minify anything, and runs rapidly, doesn't balloon the app pool, and doesn't max the CPU on the web server.