Who are the old master's of the art world ?
The term old master generally refers to European artists who were active prior to the 19th century and whose work has had a significant impact on the history of art. Some of the most well-known old masters include:

    Leonardo da Vinci
    Michelangelo
    Raphael
    Titian
    Caravaggio
    Rembrandt
    Vermeer
    Rubens
    Velázquez
    El Greco

These artists, among others, are revered for their technical mastery, innovative use of materials, and groundbreaking contributions to the development of various artistic movements, styles, and genres. Their works are still highly sought after by collectors, museums, and art enthusiasts around the world.
For each of those artists, please list the #1 painting that sold for the most money.
Determining the #1 painting that sold for the most money for each of these artists can be challenging, as the prices of some of the artworks might not be publicly disclosed, or the sales could have occurred in private transactions. However, based on available information up to September 2021, here is a list of notable paintings by these artists that have fetched high prices:

1. Leonardo da Vinci: Salvator Mundi – Sold for $450.3 million in 2017.
2. Michelangelo: There are no known records of Michelangelo's paintings being sold at auction. Many of his works are part of museum collections or in their original locations, like the Sistine Chapel.
3. Raphael: Portrait of a Young Man – The painting's value is estimated to be around $100 million, but it was looted during World War II and has never been recovered. The painting's current whereabouts are unknown.
4. Titian: Diana and Actaeon – Sold for £50 million (approximately $70 million) to the National Galleries of Scotland and the National Gallery, London in 2009.
5. Caravaggio: Judith Beheading Holofernes – This painting was discovered in an attic in Toulouse, France, and was estimated to be worth around €120 million. However, it was sold privately to an anonymous buyer in 2019 for an undisclosed amount.
6. Rembrandt: Portrait of Jan Six – There is no public record of this painting being sold at auction. It has remained in the possession of the Six family for centuries, and its value is estimated to be around $180 million.
7. Vermeer: Young Woman Seated at a Virginal – Sold for £16.2 million (approximately $30 million) in 2004.
8. Rubens: Massacre of the Innocents – Sold for £49.5 million (approximately $76.7 million) in 2002.
9. Velázquez: Portrait of Juan de Pareja – Sold for $5.5 million in 1970. Adjusted for inflation, the price would be over $37 million today.
10. El Greco: Saint Dominic in Prayer – Sold for £9.15 million (approximately $13.9 million) in 2013.