Accessories for Macbook

For some time now, just over 2 years, I have had a MacBook. I love it. It is small, it doesn't get viruses, it isn't heavy and easy to carry, but when something has to be changed, well, you really have to ask yourself if it is worth it. I had to change the battery on my former MacBook, which was stolent in Rome, and that cost €110! Today I have had to change the mains power pack because the delicate cable from the transformer to the Mac has broken, and this has just cost €89. My real question is why do these things cost so much? You can buy main power cables for very little these days!