He may or may not have that much cash but it would seem that the plate is for sale and that's the price to purchase it.
I see quite a lot of 'expensive' reg plates like 48 SV for example on a vehicle worth probably a few hundred quid if your lucky. Some 1 number 1 letter plates on a golf. Sometimes people have plates they've inherited or been gifted and that means more than the monetary value on the open market.
My mate has a very old Edinburgh Reg, he's been offered well over 70k for it but it was his grandfathers first registration and it's going nowhere.
Both myself and my mother have been contacted by people and companies looking to purchase our registrations for over 15k each, again it means more to us than to sell it. Even if I didn't have a car, my plate would be on retention.
The guy who had THE 911 lived in Bristol when I was a kid. The rumour was that he lent it to Porsche for the Geneva Motor Show for 2 weeks every year and in return they would respray and service the car on an annual basis.
I beleive he then sold it about 10 years back.