Fossil Megalodon teeth in general are not rare in some locations, but extremely well preserved and large examples are rare and can be quite valuable.  Below is some nice Megalodon tooth porn.  You can see how unique some of the colorations are thanks to different minerals leaching into them during or after the fossilization process, as well as natural things that happened after fossilization.

Photos courtesy of which has a great selection of authentic fossil Megalodon teeth available for sale.