It depends on many issues, and there is no set answer. Is the disconnect outside or inside? PVC or SEU cable? Is is a mast service? Is the panel and wiring in the house a rats nets that needs to be straightened out? Is the contractor doing it "on the sly" or getting a permit?
From my experience it can vary from $800 to 3000, even more sometimes.
The discrepancy you hear about mainly has to do with so-called contractors who don't charge enough money for the work they do. They are the ones who last a few years then disappear.