We don't post a flat price here, because what a job costs depends on things we can't know until we're looking at the door: what kind of spring setup it has (single torsion, dual torsion, or an older extension pair), whether the opener is a simple chain-drive swap or something with a belt and wall console, and whether the track or hardware needs anything beyond the one broken part.
What we can tell you is what drives the range. A single torsion spring replacement is a different job from a dual-spring set on a heavier insulated door. An opener swap on a door with modern safety brackets goes faster than one where the brackets themselves are rusted and need replacing first. And because we're driving out from O'Fallon to reach towns as far as Overland or Frontenac, roughly 20 miles, travel is a small factor in scheduling, if not usually in the quote itself.
The region we serve isn't short on households that could use this work done right - median household income across the area runs $109,049, with 88,813 owner-occupied houses among roughly 164,355 households - but we'd rather look at the spring and the track in person than guess over the phone and surprise you later.