I have worked with eCommerce packages for almost 3 years. In particular, osCommerce which is an open source website package. As well as being a very diverse shopping cart system, there are also additional modules which can be implemented into the system. For example, discount coupons, message boards and newsletter subscriptions.
When purchasing an eCommerce package, you will be provided with a full osCommerce installation on a domain of your choice. (e.g. www.example.com). See the prices page for information on costs. Also see the eCommerce portfolio page for examples of what's included in your package.