Whether it's via auction or private sales, artworks by big-name painters have drawn record-breaking prices in recent years. Some buyers are billionaire art collectors seeking a trophy piece to hang in their mansion. Others are investors with eyes on resale profit. And then there are art museums, banking that adding a Picasso or Warhol to their gallery will bring in the crowds. This list includes only the most expensive paintings ever sold, not the world's most valuable painti