I was not mistaken. I am quoting a price from the manufacturer and B&H; it's $606.
That price is for the Mamiya ring adapter ($487) and the Alpha mount adapter. You need two adapters to mount a Mamiya 645 lens to a Sony DSLR or NEX. You also need the Mamiya ring adapter to mount the lens on any non-Mamiya camera. It's an outrageous price for machined peices of metal, without any moveable parts. I'm guessing that a Mamiya licensing fee must be part of the cost. I'm sure that a Novoflex tilt-shift adapter would be much pricier.
KM7D, Sony A350, A580, A-700, A57, A65, & A5100 & bunch of lenses.