The local watchmaker here in central Iowa charges around $100 for a full service on a mechanical watch. If you like your everyday cheapo $10 quartz that you can pick up at any Wal-Mart, that's up to you, I suppose. Quartzes *are* among the most accurate of watches (the vibrations of a quartz crystal with 1.5 volts running through it are ALWAYS the same - a law of physics - so they're very predictable vs. a mechanical whose timekeeping is minutely affected by heat, humidity, gravity, and other factors) but cheap quartzes aren't worth repairing if they stop working - most cost PENNIES to build in the first place, most don't have jeweled bearing surfaces, and are really only designed to last a limited amount of time. If one lasted more than a decade in your care, you're doing very well. Cleaning it will make it last longer, but it will still wear out eventually.
Conversely, a mechanical watch is designed to last a lifetime, and there's a LOAD of engineering that went into their design. A *good* mechanical has jeweled bearing surfaces that never wear out, although even those that don't have them still function well even after more than 1/2 a century of use as long as they're kept in good repair. They get dirty, and need cleaning and oiling every few years - this is called a "servicing" and what I refer to above.
On occasion a mechanical will need a bit more work than just cleaning and oiling, and that will cost more. I'm a hobbyist in the horology field and do much of my own servicing, except on those pieces which are extremely valuable - I won't trust my own hands to do those, and am more than happy to trust a watchmaker to service them for me. It costs more, but it's worth it. It's more than possible to accidentally damage a watch while you have it disassembled for servicing (I've done it myself on pieces that I've serviced on my own), or even lose one of the practically microscopic parts - that's what watchmakers have insurance for. Certain high dollar watch brands like Omega, Rolex, Breitling, Patek Phillipe, etc., cost more to service than others. Even though the service is basically the same, the parts cost MUCH more to acquire in the event of an accident, therefore the insurance is higher. That's what you're paying $400 to service a Rolex for - the watchmaker's skill to service such a high dollar watch correctly without damaging things, and in the event of an accident, the expensive insurance that makes sure you get your timepiece back in good working order with the proper parts without paying extra.
Quartzes are okay, as long as you don't care about the work that went into them - most that you find cheap at Wal-Mart and places like it are made in China by 12 year olds in a sweatshop with no sense of quality control. Casio, Seiko, Swatch, Timex and a few others make their own quality quartz movements, and plenty of others source their quartz movements from other companies that make quality movements - for example, Citizen/Bulova buys their quartz movements from Miyota, a Japan movement manufacturer known for good quality watch movements - many of these higher quality quartz movements even have some jeweled bearing surfaces in them, but you pay more for those. You get what you pay for. Cheap $10 Wal-Mart watches are never worth fixing - I've seen TONS of them. If I throw one of those in the ultrasonic cleaner and then put a battery in it and it still doesn't work - it's parts fodder. It's not worth my time to tear it apart and find out what's wrong with it. If it's someone else's watch I'm working on, or if it's mine and I like it enough, I'll just buy a new movement for it for a few bucks and change it over. A good mechanical, on the other hand, is like a tank in comparison. There are some less expensive ones out there, but a mechanical is usually worth fixing in the event there's something wrong with it. Properly serviced, a good mechanical timepiece can become an heirloom and last more than a century.
There's a reason there are pocket/fob watches from the 1800s still around and in running condition. Good luck achieving that record with a quartz.