Carbuncle mounts have arrived!

[Arrius]

But there are no subscription costs in LoL and you don't need to buy the game.

You still need to invest quite a bit of time into League to get all champions you want/need, however.
And they make a lot of ruckus about the extra skins via promotions. I recall the PROJECT and Star guardian skins with their fancy (and admittingly well designed) trailers and login screens, basically throwing you their release in your face: "They are out, come get them! You know you want those."
Needless to say, they did cost quite a bit as well to acquire them, with Ezreal's Pulsefire skin alone being about 25$/20€.