The differences in how a watch is serviced are immense. These include:
1. How much is disassembled for cleaning. The proper way to do this is almost complete disassembly. There are a few parts that clean perfectly well in an ultrasonic cleaner without disassembly, but only a few.
2. Whether pivots, bearings, pallets, escape wheel and balance are really inspected for tolerances and damage or they are simply assumed to be acceptable.
3. Whether parts such as mainspring, seals, case gaskets, cracked jewels, damaged or worn pivots are replaced or reused.
4. How carefully lubrication is done in terms of points lubricated, quantities and type of lubrication, including the quality of the lubricant. To give you an example, the factory service "lube sheets" on a JLC 889 movement are four pages and include five different lubricants used in different parts of the watch. One lubricant, Moebius 9415 is used on nothing but the pallets. One lubricant (9010) is used on the center and third wheel bearings, a different one (8514 or 9020) on the fourth and escape wheel bearings. This issue would be an article in itself. Your repair is being done with a "lube rinse" in the ultrasonic cleaner. This is comparable to pouring a few quarts over the top of an engine, hoping that some of it will flow into the right orifices and into the engine.
5. How carefully parts are handled to prevent marring, scratching, and other damage. Proper handling means that a balance cock, as a single example, is wrapped in a fold of watch tissue before being placed in a clamp for adjustments. That quadruples the amount of time it takes to perform that one task.
6. How carefully timing and adjustment are done. This job can range from five minutes to many hours over a few weeks. (I will be discussing this in detail in the Mark XII Part Two piece next month. After overhauling and switching the 887 into the Mark XII, I spent two weeks timing it, keeping complete records on the performance and adjustments done).
7. Whether the watchmaker has the proper tools to service a particular watch or whether he makes do with what he has, which often means not performing certain tasks or performing them very badly.
8. Whether the watchmaker has access to parts and is willing to go to the trouble of ordering them. Otherwise, damaged, worn, scratched, and bent parts are simply replaced.
A proper service on a watch is about the same amount of work as a 30,000 mile service on a Mercedes. Do you think the watch should be less expensive to service because it's smaller?