Best to charge by the cubic inch, not inches in diameter. You will lose more as the stump gets bigger. I usually just eyeball the stump and where it is located, then give a price. I can usually get $350 for a 30 in. dia. stump that's cut 6 inches from the ground. No hauling of grindings, but we will move it to different parts of their yard as long as we can wheelbarrow it. I am now very willing to haul away grindings for a fee if my mini loader can get to the stump. I did it for one job....very easy work with a loader, fun even.