Perhaps the original, from Whistler v. Ruskin, 1878, a libel case in London after Ruskin dissed Whistler’s tossed-off paintings.
Ruskin: ‘The labour of two days, is that for which you ask two hundred guineas?’
Whistler: ‘No. I ask it for the knowledge I have gained in the work of a lifetime.’
(Whistler won, but won nothing.)
