I'll double check later today, but I'm pretty sure it says right on the BOA parts box that retailers are not to charge customers for the parts. In that case you got charged for labor. Changing any cable on any boa dial shouldn't take longer than 5 minutes. That's horseshit. If that's your only shop I suggest getting a dial and a couple cables from BOA directly and never dealing with that shop again for repairs. Also I'd personally go in and talk to the manager.
Go ahead, drink that kool-aid.
FS: Forum Sauce 142 $200 plus shipping
FS: Flux SE30 $75 plus shipping