I'd start off with asking them how many times they're willing to drive to an auto parts store to get yet another cheap part that will fail.
It's all about the adage, "You get what you pay for."
If the job is done right the first time, it's often less expensive than going back time and time again for a do-over.
You could also appeal to their sense of safety. Are they willing to cruise down the highway at 65 or 70 mph with critical parts that are cheap and could pose a safety issue?
-- Mark Phillips,
Editor, Counterman magazine