As a manufacturer we were able to have blown drivers replaced on Sonus Faber speakers at a slight discount for the driver parts. They still were not very cheap. As already mentioned, unless the surrounds are rotted or you blow a driver you are pretty much good to go. Bill Legal at Miller Sound in PA can fix some blown drivers and he does an excellent job at replacing surrounds. Sonus may have replacement drivers depending on how old your speakers are but they are not cheap.
Happy Listening.