At first glance, there appears to be a wide variety of garage door opener brands, but a closer look reveals that most openers are made by just a handful of companies. For example, Chamberlain garage door openers are well regarded in their own right, but the company also makes garage door openers for Craftsman and LiftMaster. Likewise, the Overhead Door Co. manufactures Genie garage door openers in addition to its own brand.
Though you can do some maintenance to your garage doors on your own, it may be a good idea to schedule routine inspections with a professional. A typical service call will include a manual inspection of the door and opener. Then adjustments can be made including spring tension, chain/belt tension, limits and force adjustments and door lubrication. Fees for this service vary from place to place, but garage door repairs typically cost between $147 and $340.
You might genuinely need some extra parts when you thought you simply needed a broken spring replaced, and a good serviceman will perform a simple inspection to identify such parts. Nor is it unreasonable for a business to charge separately for a service call versus repair work actually performed. But the best protection for you as a buyer, being somewhat at the mercy of whomever you decide to bring on site, is to understand what is being done, and ask intelligently for a clear explanation or demonstration of why extra parts are required.