How much are fish eye lenses? Which are the cheapest?

I'm gettting a nikon d3100, I really want a fish eye lense. Any suggestion?

A good fish-eye will cost more than what you paid for that Nikon body. So unless you Really have a need for one… The cheap ones aren't worth buying.

I would try renting one first, most people quickly tire of the effect.

The best full frame fisheye for your camera is the Nikkor 10.5 mm lens, about $775.

The best zoom fisheye is the Tokina 10-17 mm fisheye zoom, about $580

The best full 180 degree fisheye is the Sigma 8 mm, about $900

The cheapest is the Bower 8 mm, about $350

All are interchangeable lenses that replace your current lens

That is good advice to rent one before you buy.

Many people end up not using them after the novelty has worn off.