Ever heard of Bitcoins? It's like Monopoly money for the Internet, but it's real. That's the technical definition right there.
As it happens, Lily Allen was offered a wedge in Bitcoins to perform (as in sing) on the Internet back in the noughties, and she turned it down. Why? Because 1 Bitcoin wasn't worth €610 back in them days. She thought they were worth a load of old tut. She's since tweeted:
Today, 100,000 Bitcoins converts to exactly €60,987,972.40. She might have actually retired on that.