A great number of the people here repair stuff as a profession.
Using scavenged parts in a customer's gear
without alerting him to what you are doing
is fodder for some consumer advocate to jump on you with both feet.




On the relatively rare occasion that I repair something for money, I inform
the person if I use any used parts, and I don't charge for the used parts.
I've never had someone request to pay for new parts instead.