Clearing quotes vary wildly for the same lot, and it is almost never because one contractor is gouging you. It is because nobody agreed on what finished means. Three decisions set the price.
First, how far down. Cutting brush and undergrowth so you can walk the property is one job. Taking it to bare, mowable ground with the root mat removed is a much bigger one. Somewhere in the middle is where most homeowners actually want to land, and it costs much less than full clearing.
Second, what happens to the material. Hauling it off is the cleanest and the most expensive, because you are paying for trucks, trips, and disposal. Piling it in a corner of the property is cheapest. If you have the room and no hurry, piling can cut a clearing bill significantly.
Third, what stays. Mature trees, a fence line, a septic field, a well head, a drain line. Marking those before anybody starts is the difference between a smooth job and an expensive mistake. We walk the lot with the owner and flag them together before a machine comes off the trailer.
One more thing worth knowing: clearing and grading are separate jobs. A cleared lot is not a level lot. If the plan is to build, fence, or seed, budget for the grading pass afterward rather than being surprised by it.