I'm not sure what you're blaming Amazon for here. Are you trying to say that you should be able to freeze a sale price on something in your shopping cart?

If you're concerned with price fluctuation, let me introduce you to the greatest site I've ever found for Amazon shoppers (which has one of my favorite site names ever): camelcamelcamel.com

On camelcamelcamel you can see the price history for nearly everything sold through Amazon. Then, you can set up alerts to tell you when items drop below a certain price. It's invaluable to my Amazon shopping experience. It's how I bought my new office printer, and I saved about $30 over the price I first saw it listed for.