When we were coming up with rewards we had to think differently than most games. Axle is a mobile game and the cost of those is very different than that of a PC or Console game. We are still working out our model, but it is likely that the game will have a free version that is either partial, or has ads, as well as an inexpensive full version without ads. Because the cost would be minimal either way we wanted to give everyone willing to support the game early on rewards that would still be valuable no matter what the game costs in the market.
In short, pretty much anything that we would charge for the game would likely be less than you could donate on Kickstarter, so we wanted to be sure to include some bonuses like an exclusive level, extra watts, and other prizes to reward you guys who are willing to support us early on.