About 20 years ago, a retiring SFO 747-400 Capt leased a United 747 for a 1-hr retirement flight. He had fellow pilot friends volunteer to fill the other seat, and Flight Attendant friends volunteered to work the cabin.
It was a Part 91 flight, and he loaded up family and friends for a VFR tour around the Bay Area.
I believe it cost him about $25,000.
I thought that was pretty cool.