Valuable paintings

A painter who was old enough and famous paintings ask on display in a gallery to gallery owner.
"Is my picture attractive to buyers?"
"Yes, your painting is interested, and I said if your picture will be very valuable when you die," said gallery owner.
"Then, how?" Asked the painter..
"He bought all the paintings you, but ...."
"But what?" cut the painter..
"The buying your painting is your personal physician," said gallery owner.

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