Scrap Metal hauling ads...to be free or not to be free?

This is an interesting area of discussion amongst scrappers who are trying to increase the number of calls they get from new customers.  The question is stating in the ad if the service should be free ro for a charge.  The is some interesting psychology behind that.  For some reason, people tend to think of a fee service as being more professional than a free service.  A fee service causes one to think of business, insurance, professionalism, integrity, reliability, and speed where as a free service brings to mind an image of just some guy driving around in his pickup truck who will stop by when he can stop by, and may grab a little more than he was supposed to.  Completely innaccurate in the vast majority of cases.  SO the question is what should YOU do?  The best resonable solution that i can come up with is to state in your ads that you offer low to no fee service.  You can be the judge of what you want to charge, perhaps not charge for larger loads and just a few bucks for small loads to cover gas, that part is up to you.  The model that I have adopted, and thats not to say it is the right one or the best one, is that.  If a person has a large load of scrap metal, you will be making money off of the metal.  If they have very little, you wont make much money, however, you will get word of mouth advertising which is priceless!!