According to Wikipedia 11 paintings have been sold for over $100 million in inflation adjusted dollars. Fortunately, all of the artists represented on that short list are dead. As an artist what would you do if a painting of yours sold for more than $100 million? Try to paint nine more or do everything you ever wanted to do?
I mean I can imagine a painting being worth millions, but hundreds of millions? That being said, the Mona Lisa is so famous that the last time it was appraised in the 1960s it was appraised then at $100 million. It could quite possibly be worth a billion. Now artwork like the Mona Lisa or the Sistine Chapel are so famous and prized that I doubt their sale happening anytime soon.
Going back to art that gets sold and auctioned... Really? $100 million for a single work of art? Apparently, the actual function and purpose of art has been debated and fought over for years. There has even been an anti-anti-art movement! The point being, is art to be enjoyed by all or owned by a few? Perhaps some of both?
Art is cool. The price for art on the other hand, is often ridiculous.