I've seen them from $100-$1000. Guess it depends on how big you want. I would spend some time online looking at different ones and checking out reviews. Some of the more popular small ones go from $200-$400. Most people seem to like them with the automatic egg turners.
I just purchased a Hova-bator Genesis 1588 with automatic turner, extra quail racks and a second therm/hygrom. I purchased them from Incubator Warehouse and the total cost was $177. I ordered it online and had it in hand three days later.
I did my first ever set with the New Years Day hatch. I set 14 of my own eggs and ended up with 12 chicks, an 85% hatch rate.
I'm quite happy with the incubator and would buy another. I'll probably end up with a second without the turner to use as a hatcher so I can do staggered sets.