The price is on the rise. Last night, it was $17.09. When I got up four hours ago, it was $21.98. Now it's $24.11. You can watch it go up and down for yourself here.
I wonder if someone has invented "snipe" software for Amazon. It would be a program that constantly monitors the prices of things you buy regularly and then alerts you or places an order when an item's price hits a certain level. I also wonder how Amazon's price guarantees apply when you buy something at one price and six hours later, it's cheaper.