Sadly that is the norm, best to just let it go. Reef pretty much refuses to acknowledge that the game was even published here. Teyon probably had to pull some strings just to get the dlc launched here, otherwise that wouldn't of happened. There hasn't been a discount here in many years and I don't think that will change. When it comes down to it, it is up to whomever wants to get it here if they are willing to pay full price or not.

Hey, by all means, if you want the answers you're more than welcome to contact Reef yourself and get to the bottom of things. While you're at it, might as well contact all those publishers about the missing achievements too. No reason for you not to since you're so invested in getting this done. I will be eagerly await your findings as will many others. Do not let us down.

I have that game on my wishlist since release, I saw some incredible high discounts on Steam, but no here :/

Being on page 56 of all time best-selling here might have something to do with it. Game's been out five years. That's plenty of time to have saved the money for a DRM-free copy.