Amazon has a "post sale guarantee". If the price lowers within 30 days of your purchase, Amazon will refund the difference. Just shoot them an email. =) Here's what they say on the site: Post-Order Price Guarantee
Amazon.com's prices for released items will change from time to time based on a variety of factors. If Amazon.com's price for an already-released item decreases within 30 days after we ship the item to you, we'll be glad to refund the difference in price if you contact us. Please click one of the buttons on the right, and be sure to have your order number handy so we can assist you.
This Post-Order Price Guarantee is subject to the following restrictions:
* Applies only to products that have already been released. Products that have not yet been released but that are available for pre-order from Amazon.com are not covered by this guarantee, but do benefit from our Pre-Order Price Protection program (see section above). * Applies only to items sold by Amazon.com, and not to items (or prices) offered by other sellers on our site. * Item prices that are affected by a promotion such as "Buy one, get one free" are not eligible. * The price of an item after rebate is not considered to be the Amazon.com price.
It is an algorithm. I have seen this with other websites. Here is what you do. Look at the item then dont purchase. Close your browser and log in the following day, it will be 10% less. Happens all the time also, be sure to be logged out and clear cookies from your browser so you are a nobody when you search for items, Prime members are quoted a higher price.