Perhaps we should blame Vasari. Ever since the publication of his Lives of the Artists, and to an ever-increasing extent, the world of art has been governed by the star system. In other words, the first question likely to be asked about a painting or sculpture is whodunit? And if the answer turns out to be, not Leonardo da Vinci — as has been suggested in the case of the controversial ‘Salvator Mundi’ — then the price tag becomes enormously smaller.