Charged $870 for 'full carpet replacement' on carpets that were already 8 years old

NC law says landlords can only charge for depreciated value of carpet, not full replacement cost, if the carpet was already worn. My unit's carpet was installed in 2016. I lived there for 2 years. Their invoice showed $870 for 'carpet replacement.' I filed a response citing the depreciation argument and requesting documentation of the carpet's installation date. They settled at $180.