That is rather expensive for stuff, that could and should be considered DLC. Dammit, Ubisoft.
Ubisoft has nothing to do with it. This is all NADEO's doing. It doesn't even use Ubi's bullshit DRM.
I'm not quite sure how this is going to work, as Nadeo hasn't really announced all that much, but from what I understand, they're doing this so they can basically make a game with as many environments as they want, higher detailed and with more overall content, releasing a new one around every 6 months or so and adding onto the older ones instead of releasing a totally new game every couple years.
This is not DLC. Any of the environments can be bought as standalone, i.e. you can buy Valley without having to own Canyon or any of the others they come up with. Also, if you're like me and bought Original, Sunrise and United, and they make 6 environments for this game, you'd be paying the exact same amount for quite a bit more content and be playing just as long. Not to mention the massive community behind this who makes maps like no tomorrow, and is still making custom content for a game that was originally released 7 years ago.