Drawing on a napkin

"Mr. Picasso would you please draw something on this napkin and I'll pay you for it."  said a lady.  Picasso proceeded to draw a few lines on the napkin and gave it back to the lady, and said, "That'll be 10.000 dollars."  The lady jumped and said, "but it took you just a minute to draw this!"  "No madam, it took me a lifetime."