Last I heard was Amazon is worth around $10 billion
Second, it's a valid point that he's making. It's the same reason they post previews of video games on the game's pages. They post a 15-30 second clip of each track so people get a feel for the album, and can decide if they want to buy it. You also have to understand that for a lot of these albums Amazon sells them by the track at 99 cents each, so if somebody hears a clip they really like, they're more inclined to at least buy that track. There's a reason Amazon continues to thrive. There's a thing called Amazon Vine which I am a part of, where a select group of a few hundred people get to pick from all sorts of items every month to try & keep before they're even on the market. Stuff like GPS units, computer software, home security systems, right down to stuff like new soft drinks, new CD's and new video games. You get to select two products every month. Why do they do this? All they ask is that you post an honest review of each product you get. It's a win-win situation for everybody involved.
So it all comes down to moving units. Amazon does all the small things (posting previews & clips from albums & games), and the big things (getting the product out and having valid reviews of it posted up for when it's released), and obviously it's a winning combination.