$15 is for Pc/Mac
$20 is for Consoles
From $25 tiers, you can choose between PC version: (Windows, Mac, Linux), and console version (PS4, PS Vita, Wii U).
Physical game is only for PC version.
From $375 You get 2 copies of the game. You can choose PC (digital/physical, signed by the team) and Console (only digital).
XBOX: We don't have any response yet from Microsoft, but of course, we are very interested in ship the game in this platform soon. Let's just wait and see.
PS3: Sorry but UE4 doesn't support PS3 on its packages.