Marketing a masterpiece

I was in Amsterdam today, for a board of examiners tomorrow. I had a spare couple of hours, so I went to the Rijksmuseum, and took in some Rembrandts and Vermeers. In the gift shop they had every conceivable piece of merchandising - mugs, puzzles, fridge magnets, bookmarks, rubiks cubes, and this Nightwatch umbrella. I mean, really?