Again, that example is ridiculous. It costs the restaraunt to buy the food, the chef has to work to cook the food, the restaraunt has to pay for electricity and gas and water.
A musician has to play their instrument/sing their song, balance the audio and then it's ready for listening.
The major difference between these two examples is a musician would be making the music whether they are being paid or not, a chef wouldn't be cooking food for table after table were he not paid, a waiter wouldn't be walking back and forth were he not paid.