The more backer they get, the more stuff they can also add to the game, so give your support and pre-order now! They offer a lot of tiered rewards and also 4-packs for the pixel($15 each) and silver tiers($20 each). The 4-packs works just like in Steam where you only need to pay the price of 3 games to get 4 making the pixel and silver tier pricing to $45 and $60 for 4 games. Buy it and play together with your friends!
Check out and of course pre-order now at http://playstarbound.com/store/