Normally true, but if Amazon trade in high enough volume (which they do), turning up the price by pennies across the board will generate quite a large bump in profit. And whilst they are definitely in the low margin, price sensitive business, programs like Amazon Prime generate quite a bit of stickiness to their brand, regardless of price.

I know that I find it a pain to shop elsewhere now, not just because of price, but because I've grown so used to the reliable delivery times of Amazon/Prime. I know almost to the hour when my packages are going to arrive. That's a killer feature worth at least a moderate bump in price before I'd shop elsewhere.