Average price varies. Most are around 3.5k yen new, if you can get them from the maker when they release them. Otherwise you're going to end up paying a little more, or a lot more if you want a Mokou or Kokoro.
Bootlegs are pretty obvious, for the most part. If it looks like shit, it's a bootleg. If you're unsure, look at the seller's images compared to the MFC images of it. Use standard practices (don't buy from China, prices that are too good usually are, etc.)