Waterproofing cost is better understood as a scope question than a single price per basement. Two homes with similar square footage may need entirely different work.
The source of the water
A single leak near a pipe penetration may require a very different repair from repeated seepage along several walls.
Interior versus exterior access
Interior drainage, sump systems, and exterior excavation involve different labor, material, and restoration needs.
Questions to ask on an estimate
Ask what caused the problem, what work is included, where water will discharge, and which conditions would change the quoted scope.
What to do before hiring
Photograph the affected area and record when moisture first appears. Ask the person assessing the basement to distinguish water entry from condensation or plumbing, explain what the recommended work will accomplish, and identify the discharge route for any collected water.
If you see significant wall movement, widespread damage, or suspect an electrical hazard, arrange an appropriately qualified assessment before proceeding with routine waterproofing.