Some thoughts on reward-motivated action: it's just another way of saying people respond to incentives, and everyone does. Some incentives are psychic, others material.

Some people look at profit as vulgar or even inherently corrupting, but in a healthy exchange, there is mutual benefit. One party profits financially, like if you sell a stone for cash, but the other party also profits by gaining a good or service they value more than the money traded for it, like your customers necessarily value art they can keep indefinitely, or give as a lift, or otherwise use as they see fit. People who focus only on analyzing the monetary flow literally miss half the picture.