Free shipping

I'm shopping for stereo systems right now on amazon.com (despite my co-author's, I think farcical, assurance that "stereos are déclassé"); and, stereos being heavy, am keeping out a keen eye for shipping costs. It seems, however, that amazon.com is having some sort of free shipping promotion (I can't find the details anywhere), so now's a good time to buy. All that being said, I'm not sure what to make of this deal on a Sony stereo: