The value of art - Ostentation or inspiration?

The seven paintings stolen from a museum in Rotterdam in recent days are so valuable that the police could not immediately say what the haul is worth.

At the same time the Rolling Stones — combined age 273 years — announced concerts in London. Ticket prices reach €465, though if you fancy your dinner, you’ll have to fork out €1,180.

The juxtaposition of these stories raises an interesting question. How, in monetary terms, can art be valued?