Pay close attention to what Mary Hoeveler is saying to James Tarmy in this Impressionist and Modern preview article on Bloomberg:

“The market is very, very strong for high quality, classic works of art,” said Mary Hoeveler, a New York art adviser. “The market is as good as it’s going to be in the near future, and that’s why you’re seeing all of this great material.”

As good as its going to get for the near term sure sounds like someone calling a top.

It’s a Monet Flash Sale as Five May Fetch $105 Million in London  (Bloomberg Business)