You're quite right about me not having a Hassy rigodon777, I have very little use for one. And these are PR pics, they're in my album titled "other people's stuff".
But the 50K+? I could pick up a used Hassy H3DIII-31 like the one used here for probably $15,000 with a lens, and less than $20,000 brand new, the newer H4D-31 is going for about $14,000 with a 80mm f/2.8
You can get far more expensive cameras such as the 50MP H4D-200MS, body and back for $44,000 though...
David who? Not sure who that is, but I'd definitely be jealous. You can get get older used backs mega "cheap" right now. A Mamiya 645 digi with an older (not 80mp 180c) used back isn't too bad. The pricey part are the leaf shutter lenses.