It's full price for early access game version, and we get updates for free, until becomes release version (and beyond, but that's off topic)
As for the perks, as far as I know, nothing that won't be included in the release version as well. Unless someone considers a perk the ability to give useful (or not so useful) early feedback and having an (optional) tester contribution. These parts are a bit scary to me, because early player feedback & pressure can lead to bad changes as well, though should be mostly useful if managed well.
