It is not always a matter of being able to afford SEO teams. The big brand sites that write their own product descriptions have a clear advantage over the smaller sites. The Vince Update just started the big brand ball rolling and gave the big sites an advantage. Lots of small ecommerce sites still ranked well and drove Google traffic until Panda. Panda put thousands of small sites out of business, even if they wrote unique product descriptions.
The big brand sites will always have thousands of pages as well as a natural ability to attract links.
It is all part of a scheme to drive more small sites to AdWords--only most small sites cannot survive if they depend upon AdWords to drive traffic.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin