We know that the Magma come in the season pass, PC monster race will have a set of 4, and savage comes with preorder. Albino is unlockable, and I have heard that others will be unlockable, but there is no real or solid conformation of this. We also know that some content will be available for free through a leaked mobile game.
And don’t worry about exclusivity - when they say “limited” they mean they will be openly available for any kind of purchase one month after their “limited release”. Time exclusives only. The only content exclusive thing is a special set of turtle rock skins for Devs only.
As for skin pricing, it is “TBA”, so no word on values yet.