We don't publish a flat price for spring or cable work sight unseen, because the correct spring wind, door weight, and whether a drum or cable also needs replacing all change the number. What we can tell a Severna Park homeowner is that a single-spring torsion setup typical of a 1978-era door is a more straightforward job than the double-spring, heavier-gauge systems on newer construction, which usually keeps the labor side simpler.
What drives cost up on this specific job is deferred wear - if the drums, cables, and rollers are all original alongside the spring, replacing just the spring and having it fail again in a year isn't worth it. We'll say so on-site rather than sell a partial fix.