Oh, Banksy. Always bang on the money with your witty observations (although – ironic art fact! – this oil on canvas swipe at consumerism didn’t actually sell when Sotheby’s tried to auction it in 2008). We are totally obsessed with sales, which is why it comes as no surprise that everyone from Buckingham Palace to the 99p Store chain is knocking off money quicker than the late Ronnie Biggs (incidentally, how do 99p Stores have sales?!).