If you are a lucky MSDN Universal subscriber then you can get Expression Encoder (released yesterday with Silverlight 1.0) for free. How ?
Juts use the key you have for Expression Studio delivered on MSDN Subscriber Downloads, on the page Subscription Product Keys.
This was posted on the newsgroup
We are pleased to offer Expression Encoder, formerly Expression Media Encoder, for download. If you are an existing Expression Studio or Expression Media customer, please enter your Expression Media (Windows) product key when prompted during the Expression Encoder installation to activate the software. If you do not have a product key, you can download Expression Encoder and preview its functionality. This fully functioning version will expire 60 days after installation. -- Jonathan [MSFT]