Buying Brains

This joke takes place in the very distant future, so distant that shops exist where ordinary people can walk in and buy the brains of famous people from the past.

Three guys walk into one such shop and begin to look around. The first guy spots Michael Jackson's brain on the shelf, so he asks the cashier "Hey, I see Michael Jackson's brain up here. How much do you want for it?" The cashier says "How about 25 thousand?" The guy pays accordingly and walks out with Michael Jackson's brain. The second guy sees Stephen Hawking's brain on the shelf and asks the cashier how much it will be. The cashier says "Mmmm. How about 60 thousand?" The guy produces 600 bills (Hammerspace exists here too, ok? ;D) and walks out with Stephen Hawking's brain. The third guy sees Donald Trump's brain on the shelf and asks "Hey, I see Donald Trump's brain up here. How much for that?" The cashier replies "Oh, that'll be only 6 billion dollars" The guy, knowing his hammerspace can't hold that much money, utters in disbelief "What!? There's... there's no way that can be right!"

The cashier replies "It's in mint condition. Never been used"

Source - My dad. Made it up on the spot.