If you're short on dirt, I know a couple of tricks some guys have used.
One got hold of wrecked cars and used them as the foundation of the jump, then piled soil front and back and on top.
The neatest idea I've seen was on a wooded lot. When the trees were cleared, they were cut into logs about 8 feet long. Wherever a jump was put in, the dozer cleared the stumps and dug down (I think it was 4 or 5 feet) and set the soil aside. The logs were then laid in the hole/trench and even stacked higher than ground level -- in the shape of the required jump, but smaller over all. Then the dirt from the hole was spread and packed on the logs. Enough dirt left over for whoops, and berms.
I guess as the logs rot, the jumps may "settle" a little, but it won't take much dirt to patch them.