How much actual use would these lenses be to anyone ?
Well, Charlie's Super-Q Gigantar was a colossal joke, not a lens to be used. f/0.33 is impossible in air. The Barry Lyndon lens was used for very low light cinematography. There's a scene in Kubrick's Barry Lyndon that's lit by one (1) candle. f/0.7 was useful then and there. Necessary, even.
I don't think the link mentioned the monster 1700/4 lens Zeiss made to fit a Hasselblad owned by a ruler of one of the emirates. He was an avid wildlife photographer, had the funds to buy a very expensive one-off and a vehicle to transport it.
Ben, isn't it interesting that its often the poor who support sumptuary laws?
Fotch, still photographers have rather strange concepts of expensive. When Arri introduced their 535 35 mm cine camera the price was $250,000. Their market was rental houses, not studios or directors of photography. The better grade of lenses to fit cine cameras (from Cooke, Panavision, Zeiss, ...) are unbelievably expensive. Again, the real market is rental houses. I've seen po' folks toting Bigmas and monster Canon lenses in the Everglades. Keen wildlife photographers. I don't watch TV much, watch football on TV even less, but every once in a while I watch a game with my son-in-law. Lotsa huge expensive lenses on the sidelines. I b'lieve they pay for themselves.