In Larian's case, if they add alpha/beta access to the Larian Vault for non-kickstarter backers to purchase, there wouldn't be the same sticker shock of it just showing up on Steam (most people would know in advance that there was a kickstarter and what the add-on prices were set at).

Personally, if I backed Planetary Annihilation at $90, I'd be rather annoyed if the developers listed early access for cheaper. I didn't read the discussion you linked to, but I see all kinds of games listed at prices higher than I am willing to pay. My reaction is to simply not buy the game, but wait for a sale or price drop, or both.