I just got an e-mail letting me know of a 50% off promotion (for US residents) at the Microsoft Store on the Expression suite of products, including the entire Studio as well as the stand-alone components, Expression Web and Expression Blend.
So you can get Expression Blend - the sine qua non (ok, so I'm a Latin geek) for WPF and Silverlight designers - for $250, or the entire Studio for just $100 more (go ahead, you've been good this year, right?). Expression Studio, by the way, includes
For those of you wanting a longer term investment (and have a little more spare change!), keep in mind that there are MSDN subscription programs as well that include some or all of the Expression products: