The honest answer is parts, the size of the door, and how much of the job is labor versus hardware. A single torsion spring swap on a standard door costs less than replacing both springs plus cables and rollers on a double door that has not been serviced in years. On a spring job we also recommend a full cable and roller service, since the labor to reach them is already done and it saves you a second trip later.
With a median household income of $74,778 across this area, most people we talk to want the repair done right the first time rather than the cheapest patch that fails again in six months, and that is usually what we recommend too. We are not the lowest bid in town and we will not pretend to be. If a door's track is bent, the opener is a decade past support, and the panels are rusted through, we will say so and tell you replacement costs less over time than another round of repairs.
We also will not give a flat number over the phone, because a door from the earlier end of the 1966-1997 range often needs hardware a 1995 house never had, and some of those parts are special-order. When that is the case, we tell you the lead time before we start.