It wasn’t installed wrong, it was improperly installed. I find it odd that the other mechanic didn’t just tighten the terminal for you.

Customer pay was (book*1.5 + diag if applicable). Electrical was 2 hours diag, plus straight time. Location of the repair could add time, too. I really hated having to call customers about fixing their shit. The tech job was much better.

Edit - worked at a GM dealer years ago