The One is absolutely correct about charging for everything. If your store gets the reputation as a give away store people will come in and expect to get services for free. I once worked for a dealer that only cared about sales, if someone came to him with a complaint about a service/body shop visit he took care of the bill. It didn't matter if you had a legitimate complaint or not if you didn't want to pay for the service just go see him and complain.
In reality a freebie can get huge returns if given to the right person. The key is knowing which person will APPRECIATE the gesture. If you don't feel you can pick the right person for a freebie follow The One's school of thought and you will never go wrong. A discounted price can carry just as much weight as a free service and is easier to get the appreciation factor. If the customer doesn't appreciate the gesture it is just lost profit potential.