When you receive call to your toll free number originating from within your own state, you pay a different rate than you do from out-of-state callers.  These rates vary from state to state because of the different tariffs in each state.  

Unfortunately each state has the right to tax transactions which take place entirely within their state.  This is an over simplification, but these fees ultimately get passed on to the end user.  They may vary slightly from carrier to carrier, but only slightly. 

This is why I set up InState800.com.  It's a special service that can get around these higher instate rates by routing calls out of state and then back.  If most of your calls are from within your state, and your rates are significantly higher than the InState800 rate (5.9 ¢ / min) you should try InState800.com.  But if you market nationwide, probably only a small percent will come from your state so the lower Out-of-State rate here will be better for you.