Everyone start getting on same path, that content is the king, so many posts about that, but if you look at the great shopping sites ( big dogs ) with tons of the traffic, they don't have any content or very small amount or short descriptions of the products, so, how does those sites gets so much traffic, just because they BIG? For example if you have nice description of the product with bunch of words, which no one reads, its not value for customers, the value for the customers is to see very short exact infor of the product. so, it less words but more value for customer, which has to be value for google,( as they saying ). so, text on page for products has to be balanced, and i don't think, if you have 300-500 words text per page will get you anywhere just because its original content, which no one cares and read, i dont think so.
They get traffic because they do seo and also service sites get traffic easily than any blog.If your content is original and fresh people will surely read it. Always remember content is king next comes link building.if your content is good automatically others will link to you, getting you natural backlinks.
Also big name retailers have thousands upon thousands of web pages, Google reward them with a high PR and so they rank for keywords with little to no work. It's a round about way of saying google will push them to the top because it is what people want when they search. That is Googles whole aim.
As James Lennon says, ignore the big boys if you can´t compete on their level gifted to them by google. Find your own path to building wealth in which they cannot. For example that might be more in-depth reviews or a more personal feel, qualities they those guys can´t compete with.
Google likes not just description or 300-500 words texts. The best materials is analytics or market (goods) analysis or review with comments and feedbacks. If it is unique than there will be traffic.