In response Amazon did a lot to reduce price transparency. If you notice now most categories of items are constantly 'on sale' and even if camelcamelcamel picks up that fact, there are also 'coupons' available on-site for most amazon products that only alter the price under certain conditions and they're only applied at checkout.
This makes it difficult for a human being trying to buy things to compare the prices, let alone a series of scripts.