A fair estimate explains what could change the price before the work begins.

Any job has unknowns, and the honest question is not whether the number might move but who learns about it and when. An estimate that names the conditions in advance leaves the customer able to decide. One that stays quiet hands them a surprise later, at a point where refusing has become expensive. The difference is not accuracy but disclosure.

Say what would push the figure up and roughly by how much, before anyone commits. If you are buying, ask that directly and get the answer in writing.