I was reading a blog entry the other day that asked what had happened to the Microsoft Zune, the much touted rival to the iPod. Given the money Microsoft spent promoting the product it is a good question to ask. One way I sought an answer was to look on eBay and see what price these were now selling for. In essence I wanted to see if there was a big market for them and also what had happened to prices. It then occurred to me that eBay in effect offers a great tool for people wanting to track the life cycle of a consumer product. You can pretty easily take off the current pricing of products (highest and lowest) and also the volume available on a daily basis and thus plot the rise and fall of these products over time. This is the sort of data that usually required expensive research. Thanks to eBay it is essentially free if you can get someone to pull the data, or if you create a tool that automatically takes off the data. In the case of the Zune it did sell at a small premium to start with and can now be bought for around $180, which is about a 28% discount. Taking my theory another step I’m pretty sure you could use this kind of data to predict when you need to release a new version of a product in order to prevent the sales price sliding too far. Of course you could also use it to predict when your competitor should be releasing a new product.