We had one as as kid. We covered it every day, even during the summer, once we were done using it, and that cut down on the upkeep part a bit...not so many leaves and stuff to have to fish out of the pool. These days, the solar covers seem to warm them up a bit more, if you don't have a heater...at least accoridng to my DBIL who currently has a pool.
Upkeep not unbearable but I would recommend you keep up with the upkeep, or it becomes very difficult. Pretty much every day we skimmed the pool several times, vacuumed it regularly, checked the chemicals several times a day. My parents were religious about making sure that chemically the pool was always in balance...they always bragged that no one ever got an ear infection in our pool, whereas, back then, a lot of pools caused ear infections. Our water was always crystal clear. My parents did have us kids do some of what we were capable of doing, depending on size/age. We all knew how to cover the pool from Day 1, and as we got older, learned how to test for the pH, skim and finally vacuum. My father usually handled most of what had to be done with the filter though...flushing it and so forth.
For us it was well worth the effort.
As far as cost, I would have no idea because it was 35 years ago that I was a kid!
I'm not sure I think spending $5000 as opposed to $20,000 on a pool is being "cheap". As kids, we had just as good fo a time in our 18 ft.round pool as we did when we went to someone's house who had a built in.