If it's a question of priority then their priorities are backwards. Keep in mind that the game isn't supposed to be delivered until April 2015...and that's if it's on time (How many overfunded Kickstarter projects have actually been on time? All those stretch goals typically require extra time, not just money.). So why is it that there's a $1.1 million gap between PS3/360 and PS4/XB1? By the time this game actually comes out the PS3 and 360 are going to be old hat. And it's certainly not the difficulty of porting, since the next gen uses a PC-like architecture and Sony and MS are bending over backwards trying to get devs onboard. There is every indication that the PS4, at the very least, is a lot easier to develop for than the PS3.
Also, there's a reason ports to different systems are typically relatively low goals in most Kickstarter campaigns. More systems means more potential sales when the game comes out. It's not just about the people who backed the Kickstarter, they can make more money once the game is complete. Developers usually want to get their games on as many systems as possible, it's just a question of whether or not they have the resources for it.
No, the only logical explanation I can see here for why they placed these stretch goals so high is that they're trying to use them as a carrot to entice people to donate more. You want the game on PS4? Then you have to donate more! And tell all your friends to donate too! It's marketing, essentially...
And that's BS.