Roof leak repair costs and affected layers
A small visible gap can require opening surrounding shingles to restore the failed flashing. A larger-looking shingle loss may still permit a localized repair when the base and adjoining covering are sound. The size of the indoor stain is not a useful roof-repair price unit.
Access, the failed connection and damaged wood or wet layers determine the scope. If repairs keep recurring across a broadly worn roof, the meaningful budget comparison is another local repair versus the replacement work that corrects the underlying condition.
See roof repair for those mechanisms, and roof replacement for the complete sequence.