Yes the pool, tennis courts along with any other ammenities all fall into the monthly maintenance fees for condos. Usually the higher the fees the more ammenities are involved. $280 is not bad at all I used to pay $425. per month. The ammenities along with the building and property all need to be maintained and insured and usually the building insurance is the highest expense the complex will have, but you will still need to insure the inside of the unit.
Hope this helps, best wishes.