I just love when people call me and pretend to be a customer...just to find out my rates.
In my humble opinion, it's intellectually dishonest and it wastes my time calling someone back or taking a call from someone who doesn't respect my time or lies to me.
Generally, the market is what sets the rates but why just work for market rate? Research what your costs are, learn to provide exceptional service (it takes a long time to become efficient and do a "pretty" job mulching vs just blowing and going through property). When you are good at what you do and reliable, you can charge what you need to in an order to make a profit. I am not saying you can gouge someone, that too, would be dishonest, but there is nothing wrong with making a profit instead of working for the going rate and competing with guys who will lower their rate by a few dollars because you charge "x".
I have been mulching for 10 years and running my business since '97 and don't care what my competitors charge. If I did, I'd be out of business trying to match the fly-by-nights who get into this line of work "to make a killin'" but don't consider the long-term. There is always going to be someone cheaper...or someone using an inadequate machine that will leave half-mulched trees and stumps. Charge what you must to make a living and provide an exceptional level of service. If it is too much, the market will let you know. If it is higher than the competition and you are getting work, then you are doing something right and should keep doing it.
Again, it takes awhile to get things down to a system and then it still gets screwed up now and then. Try teaming up with an established mulching contractor and work and learn with them. You might end up with more work than you can handle and not have to go through the same learning curve some of us independents had to go through.
Good luck.