To answer your question, yes, the game and DLCs go on sale periodically, nothing super crazy, usually topping out at about $5 off or so.

In the spirit of teaching a person to fish and all, you may find IsThereAnyDeal useful. It's got price histories for most platforms and key vendors* and if shopping sales and bundles is your thing you can set up email alerts.

* personally, I like Fanatical or Humble, (and Steam) since their keys are all nice and official, but if you're grayer markets are your thing those are there too