If fast food places gave cashiers 1% of the orders they rung up back as a bonus, they'd probably see productivty and upselling Skyrocket. They'd tell all their friends and family to eat there and would be super motivated. It could easily pay for itself.

This could be an alternative to raising minimum wage. It would give them a raise but make it contingent on their performance and how much money they bring in the company... and would allow them a base pay with no set cap.