If you do not know your operating costs at this point, and are trying other methods to find your pricing I would look at a couple of things.
1. What do other people charge doing similar work in your area ie, if you wanted to sub it out, what would it cost you to have it done?
2. What the rental cost of that machine would be, and what the minimums etc would be in your local area.
3. I am assuming you are operating above board with reference to taxes / insurance, licenses etc. It sounds like you are just starting in and getting a feel for it, but I will caution you that when you tell someone the price, remember that you will see between 35% to 50% of that price come into your pocket after taxes etc. Then you still have to pay your expenses (gas, maintenance, what you broke etc.) before you put any $ in your pocket.
It is very tempting easy for folks starting into a business like this to say, something along the lines of well, I was making $10 an hour at Wally World and I own my machine so if I charge $20 an hour I am making twice the money, all those guys out there charging $50 (or whatever) are ripping people off..... After they have been around for a while, they find they are charging those prices as well, or going out of business.
There will be a wide range of rates being paid, a general Contractor having yards done as a normal deal will pay a lot less then the one time homeowner who needs some quality work done.
I would talk to some landscapers in your area, we have a 610 Bobcat and a NH 1925 and we sub out a lot of our dirt work to a guy that we work with for $50 an hour. It is just more practical sometimes for us to pay him and have it done than for us to do it with our stuff. He has a Harley as well as a substantially larger Gehl Skid steer.