As cheap as human life is in a bike shop, repair costs still mount up quickly. As beer costs rise, so does the cost of labor. And parts aren't getting any cheaper, either.
Faced with a repair estimate of a hundred or two hundred dollars, customers will say, "for a little more I could have a new bike."
Yes and no. If you paid about $300 for your bike 15 years ago, it may have componentry as well made as on some bikes selling for $500 today. And if you get your bike serviced by a shop you will definitely spend more on repairs over its lifetime than you plunked down to buy it originally. You can't think about it just in monetary terms.
The more you can fix yourself, the more money and time you will save. Buy tools and parts.
I suppose most readers here know this, but I'm used to writing for papers where I hope the less sophisticated rider will read. I want them to outgrow me. I want them to stumble on this blog as source of information and a slice of life.
Bikes aren't like cars. For all the efforts of Shimano, there aren't a lot of mysterious, complicated systems in there. If your Wonder Shifting bites the big one you can always put on Stone Age Shifting and still have a bike to ride. That's not an option with your car. So in bike repair you have many routes to the single destination of a ridable bike. It may not be exactly the way you got it on the first day, but you will be able to get around. You have to decide how much you want to cling to the original configuration, or how close you can get to it with available parts when it does break.