Avoiding duplicated links

The global navigation on Amazon.com normally shows a "Cart" button including the number of items contained in the Cart (click to see full-sized image):

However, when a user is viewing their cart, the button (kind of) goes away:

The button is still there, but the label is gone.

This is an interesting solution to a common design problem, which is handling global links that are redundant or potentially confusing in a specific context. The goal here is to direct the user to the cart-related links in the main content area of the page. I've not seen this done before, but it seems like a reasonable solution.