It's about the cost of MFs for one of my high MF timeshares. Costs will depend on where you live and what all your pool has.
Here's some of the things we have that go wrong:
Electric pool cover gets stuck or stops working. We have the company that installed it come fix it. $125 minimum charge, goes up if I need to buy parts.
At least once per year, the solar heater leaks and needs repair.
We started out with a salt generator, but found those need to be replaced every year or two so switched to chlorine, which I hate.
Our fancy pool light that changes colors stopped working after 2 years. I've never had it fixed because I saw a story on the news that says there are a lot of deaths from sloppy workers who don't change out lights properly and people get electrocuted.
Our pool pump is one of our most expensive electricity items. I wanted to switch to a different one, but my husband's best friend runs a pool business and said the other kind are full of problems. So, my husband has a melt down whenever I mention switching it out to save on our electric bill.
I usually have 4 - 5 months where I use the pool often. Our pool is very large and it's too difficult to heat during the cooler months. Even though I use it often in the summer, in the other months, I often think about filling it in with sand and using that money for something else.