i'd be getting a lot more than 10 cubes of dirt to start with, one good reason being that the expense is in the transport of the dirt, not so much the dirt itself, i'm talkin around 60-70% of the cost is in transport. having said that if you're paying for a truck to bring dirt to your property, you might as well tell them to fill that sucker to the brim to make it worthwhile. not too sure exactly how a cubic metre of dirt compares to a tonne of dirt, but i believe they're very similar. i have over 120tonne of dirt in my backyard for jumps, and trust me it doesn't go very far. it looks like a lot when it's first delivered, but once you start forming the jumps and packing it all down, it disappears very quickly.