An alternator that has stopped charging usually has worn brushes or a dead regulator in it. A starter that clicks and does nothing usually has a solenoid or brushes. In both cases the failed piece is small, cheap and replaceable, and the rest of the unit is fine.
So we strip them on the bench, fit the small part, clean out what a decade in this climate leaves behind, and load test the whole thing before it goes back on. That costs a fraction of a new unit, and it frequently outlasts the cheap replacement units sold here, which is not a compliment to those units.
When a rebuild would be dishonest we say so: an open circuit rotor, a case that has been under water, bearings that have taken the shaft with them. Then you get the price of a good replacement and the price of a cheap one and a straight answer about the difference.
Every rebuild is tested under load in front of you if you want to watch, and there is a two year warranty on our own rebuild work.