For me, the cost would probably have to come down around $200 before I would consider one. But I don't have a specific use for one. A prototyping business is probably already well within the necessary ROI for owning one (or many).
The speed for doing the printing might also have to improve before home consumers would want one. My Mom is a "Crafter", and I know she would love one of these things (far more than I would), but it's still not worth $1000 I don't think, even for her.
Home Versions: around $1000
Pro version MakerBot : $2189
Here are a few more videos with examples:
Download plans for stuff here:
http://www.thingiverse.com