>>723583387
It's worth whatever people will pay for it because there's a record of what other people paid for it in the past. People will buy it on speculation that it will retain value or increase in value. This is how the art trade works.
Art buyers don't actually believe some bullshit on a canvas is worth $2 million dollars from an artistic perspective. They buy it because it doesn't depreciate, they can insure it, they can take it anywhere they want, and they can sell it again for at least as much as they paid for it. Try to fly anywhere with $2 million in cash and it will get confiscated immediately, but you can easily fly with a painting. Think of it like a $2 million dollar bill.