the price rose 4$.
Amazon does that. They reprice items on 15 minute window. If a product gets some attention (your page hits is enough), the price goes up. By linking an item to a post here, that could increase the page-hit-rate.
You can make it work in your favor, however. Wanna save a few bucks? Find something you want, then clear your cookies. Look where they tell you what other people bought after looking at that item. Hit those pages once an hour for a few hours. Then go back to the thing you really want and the price will (often) be lower, while the things whose pages you were trolling will be more expensive.
You can, on a much slower/longer time scale, do the same thing by putting something in the save-for-later area of your shopping cart. Ignore it for a few days/weeks, add something completely unrelated to your cart, and Amazon will tell you that whatever was in your save area has decreased in price. Add the thing from your save-area of your cart to lock-in the price, delete the thing you added that you didn't want anyway (but only added to get them to reprocess your save-for-later stuff), and profit.
TL;DR: The price went up cause Mr. Bezos knows you will probably buy it. Convince him otherwise and the price will go down.