OfficeSharepointPro.com reports that SharePoint Designer will become a free download from microsoft.com starting April 1st!  If you visit the SharePoint Designer site, it is still listed as a purchase at $299/upgrade at $159. I have not seen the official Microsoft word on this, but I have seen a few other blog postings in addition to the one at OfficeSharepointPro. Sound like a great offer. if I were planning a purchase, I would wait until April 1st or until the official notification is released to the public.

Microsoft says it's making this change in order to help customers get the most value out of their investments in SharePoint Products and technologies. 

Beginning with the April 2009 Volume Licensing price list, SharePoint Designer will be removed. 
 

[UPDATE]

Microsoft has posted a Letter to SharePoint Designer Customers

Published: March 30, 2009

Dear Valued Customer:

One frequent comment from you to us here at Microsoft is that a significant part of the capabilities of SharePoint Designer are seen as just an extension of what SharePoint already does. In addition, we hear more and more that you want to be able to create increasingly dynamic web sites on SharePoint.

• In response to this feedback, we are implementing a number of changes to promote and facilitate even more customization efforts on top of our platform: Starting on April 1, 2009, we are making SharePoint Designer 2007 available as a free download.
• Customers with SharePoint Designer 2007 Software Assurance (SA) current as of April 1, 2009 will receive upgrade rights to Expression Web for the lifetime of their SA agreement.

Read the rest of the letter at the SharePoint Designer site and download from the Microsoft download site.

[/UPDATE]