When Leonardo da Vinci painted the Mona Lisa he couldn't have realized it would become such a famous painting.
Prior to 1911, it was housed in the Louvre. Then the painting went on loan, only not in the usual way. An art thief took it home and stored it in the base of a trunk for approximately two years. He served seven months in prison for taking the portrait, and probably increased the value of the smiling lady due to the additional publicity of her theft and return.
He definitely increased her security detail.
I imagine the ghost of Leonardo walking into the Louvre with all the other tourists, and having a smug smile on his face as he looks at his work. And then probably shrugging off the value, shaking his head, and going to look at the other artists' work.