Limit orders for eCommerce?

In the stock market you can create ‘buy orders’ (also called “limit orders”) which allow a trader to set an automatic ‘rule’ to buy (or sell) a stock when it reaches a specific price. So why not have that feature on Amazon, JCPenny, Staples, Sony – or a 3rd party site that will do the buying for you? Imagine you want that SuperTooth Disco High Power Bluetooth Stereo Speaker, but you just aren’t willing to pay $103.81 for it… but you WOULD pay $85. Sure, you can shop …