You'll find the Price Trends page in the Tools menu. It's free to use, even without an account.
Choose products or cards, a game, a period and the direction of change: rises or drops.
Tiles above the ranking show how many items went up and how many went down in price this week, how many are above their 30-day average, and how many hit a 30-day high or low.
Clicking an item opens a window with its price history.