This brings up an interesting legal issue...
https://www.quora.com/Why-isnt-fraud-free-speech?share=1
https://www.npr.org/2012/02/22/147257716/is-a-lie-just-free-...
https://pomlaw.com/monitor-issues/free-speech-vs-corporate-l...
If he had just said he thought the art was worth this much. He would probably would have been fine.