The story we got during the kickstarter was that they sold Defense Grid too cheaply. When it came out, indie games were still kind of new, and I don't think anyone had really set a price point.
Also, Hidden Path isn't really like a 5 man studio or something, there's a lot of guys that work there, so selling a game for like $5 isn't gonna cover a lot of bills.
And one other note, the kickstarter didn't fail. It just wasn't funded to a million bucks. Their plan was to use the money they could get to make a DLC, which would make more money for them, which would help finance the sequel over time. And yeah, everyone who chipped in to the kickstarter still gets a copy of all DG material. I've had Containment since before launch. Pretty good TD, can't wait for the second to get to beta to try it out.