Microsoft recently announced prices for Windows Anytime Upgrade and Family Pack Pricing.
Some of the details from the Windows 7 Team Blog…
Windows 7 Home Premium to Windows 7 Professional: $89.99
Windows 7 Home Premium to Windows 7 Ultimate: $139.99*
* You’ll note that we’ve reduced the price of moving from Home Premium to Ultimate 12% in the US as compared to Vista pricing
For more information visit the Windows 7 team blog