Steam Alerts will notify you via email when a game goes on sale/or drops below the price you set. Its extremely easy to use and request 2 steps.
Now your going to tell me steam already does this right? Well kind of. They will just notify you via steam when it goes on sale. Not determined by your price.
1. Find a Game
Begin your search right now!
2. Set a Watch
Select a game and enter in how much you’re willing to pay.