It's art he can't live on

From Travesties by Tom Stoppard:

CARR: Art is absurdly overrated by artists, which is understandable, but what is strange is that it is absurdly overrated by everyone else.
TZARA: Because man cannot live by bread alone.
CARR: Yes, he can. It's art he can't live on.

. . .

JOYCE: You are an overexcited little man, with a need for self-expression far beyond the scope of your natural gifts.