Here is a fee calculator, you can adjust with free vs. shipping cost and see what the difference is. For example on a $50 item sold you save about .50 cent in fees if free shipping offered....
http://www.newlifeauctions.com/calc.html
In my opinion, reasonable chipping with "free or reduced" shipping for multiple items is the way to go i.e. $2-3 for first item, the rest .25/ea kinda thing...
I don't see that as a seller that I should pay shipping out of my pocket.