As we journey through life, there is every need to step back as the artist does for a better perspective. Which is better, to give the farmer who engages in a back-breaking job or the waiter who waits in a comfortable restaurant a better tip.
The farmer offers to sell his or her produce without recourse to having the undue advantage, while the restauranteur pry on man's ego to be big and seemingly generous.
I think if anyone between the two needs a tip or a better tip, it is the farmer, and there should be no haggling of whatsoever with them, for there were lots of sweat that went there before the produce.