Consider as well that a good deal of the game's engine is already finished and they are now building the levels and working on debugging the character classes. They are also going to be releasing the alpha within the next couple of months. As a point of reference, Guild Wars 2 entered closed alpha around a year ago and is almost ready for release. I'm not saying that Grim Dawn will be out within the same time frame (smaller team) but it illustrates the point to some extent. This game is already on a path toward completion.
Unlike other games on Kickstarter, Grim Dawn has been in development for a while now and they've got a lot to show for it. Additionally, they've been collecting funds via their own website for over a year now. Since Kickstarter has become popular, they've decided to try it out as a source of funding as well. So I wouldn't worry too much about the smaller sum of money they're asking for. Because to put it simply, they've got less work to do than others, which I find reassuring. They've already got a product, not just ideas.
Check out their website
and cruise through the forums and have a look at what's already been done.