Without stating exact values, to the best of my knowledge, vehicle parts can only be repaired to a certain condition, and no further than that. However, the estimate verb will still give an estimated price to repair for parts in that stated condition, even though they vannot be repaired any further. This skews the actual repair costs and can be easily confusing for someone who isn't aware that it's happening.
Would it perhaps be possible to take this into account with the verb and perhaps recognise that condition as the base level for not needing repairs?
WAGE SLAVE