If you getting a working line GSD pup and both the parents are from working lines or champions, then yes anywhere from 15K to 25K or more you would get a pet quality GSD pup, which does not have any fault but would not qualify for show purpose and I believe you or your friend is not looking to show the pup and would be at home. Show quality GSD would cost anywhere between 30K to 80K.
Also I believe, getting a pup from reputed breeder is Important, background check is really important when you talk with Breeders, ask as much questions as you can, see what comfort you get, weather the breeder is able to answer question sharing all details. Do not entertain brokers or dealers.
You might get a GSD at cheap rates but the behavior might not be of a GSD when they grow old, or might not be healthy. Please browse thru. many such questions/ answer on this blog which might be helpful.
As far as Rotty is concerned, its much expensive as compared to GSD, anywhere in excess of 30K it would cost.