Yeah, there is indeed a fisheye lens that sells for $67,000 on [shoplink 53007 ebay]eBay Canada (Click here)[/shoplink]. It’s the Nikkor 6mm lens and this is how it look son your A7/r/s camera. That is what the seller writes:
This Nikon 6mm Fisheye-Nikkor F2.8 lens outfit is in mint like new condition. Serial #629436. This is the real deal. A legendary lens from Nikon that is in very low production number. Exact production number of this lens is unknown as it was produced by special order through the Nikon catalogue. This is the world’s most extreme wide angle lens at 6mm! First introduced in 1972, it features a super wide view of 220 degrees. This lens can literally see behind itself!
Gossip aside, I wonder if Sony actually has a FE fisheye on their lens roadmap. Or maybe they will stick with the use of FE Fisheye converters.