a couple of rooms in my house are at 14 and 17 feet, but nothing up to 25 ft.
we have painted all the walls in the rooms at one point or another.
depending on how adventurous you are, you really could do it yourself with a tall ladder.
even with purchasing a big ladder and all the tools, i have got to assume you are going to come out cheaper then paying a pro. plus then you have a huge ladder so that you can send James up on the roof, to clean gutters, etc.
that said. we have popcorn ceilings in most of the house. and before i moved in i DID pay a pro to come in and spray all the popcorn ceilings for me.
it was very nice just to have it all done in like 2-3 days and only have to write a check.
if i had to do it over again though, i would have paid even more to have a pro come in and pull all the popcorn down.