[The Artist Formerly Known as Hawk]

And apparantly, the blink power recharges, so actually has no cost. This is deliberate, as they didn't want you to be able to blink somewhere and get stuck, which, you know, happens with powers like that. On thinking about it though, they do seem to be contantly topping up their mana in those vids, which I doubt you can do quite so much in the full game, so they've probably got god mode on there giving them unlimited potions or whatever. Plus they did build the level, so they obviously know the best way to easily complete it and they are only playing on normal.

Other powers do seem to be more draining, like possession, which takes a massive amount of mana to use, so you're probably not going to be able to spam it.