Well, I've just run through the same gauntlet because the company I work for is making the shift from Office 2002 to Office 2010 (hello ribbons...).
I think you'll find that unless you are willing to risk buying a pirated copy of e-bay or other questionable websites, the prices for Office 2010 are depressingly consistent. Compared to the B&M chain stores, you can get a small discount on sites like Amazon or Newegg. The best deals by far are for the academic versions provided you qualify (which I do not).
I ended up going "all out" and purchased an Office Professional 2010 Product Key Card for $350 at Staples (1PC). I used a 20% off in-store software purchase coupon to bring the price down to $280.00.
http://www.staples.com/sbd/cre/marke...are/index.html
That was the best I could find right now. Good luck!