"WILL you never learn, my dear, the difference between real and
exchangeable value?" The question was put to a husband, who had been
lucky enough to be tied up to a political economist in petticoats. "Oh
yes, my dear, I think I begin to see." "Indeed!" responded the lady.
"Yes," replied the husband. "For instance, my dear, I know your deep
learning, and all your other virtues. That's your _real_ value. But I
know, also, that none of my married friends would swap wives with me.
That's your _exchangeable_ value.