The staging servers has been deprecated by Microsoft, including their token service. The good news is that it has gotten a lot simpler now. Instead, go to www.bingmapsportal.com sign up, log in and generate a token/app id. This token doesn't expire.
Now all you need to do is set the token property on the layer:
<bing:TileLayer Token="[your token goes here]" />
You do not need to do anything on the server to generate a token. Also note that staging server is not supported with these new tokens
At the front of the bing maps portal it says:
For information or inquires about pricing, licensing or volume licensing, contact:
maplic@microsoft.com .
Also if you go to the bing maps website and click licensing you can find the following:
http://www.microsoft.com/maps/product/licensing.aspx