Depends on your viewpoint I guess.
Did you get a written estimate up front so you knew exactly what you were paying for?
Did you discuss the install, what he was going to be doing, what materials and wire, etc before you agreed on the $120 estimate?
What kind of car is it and how much modification was required to install the speakers? If a lot of mods were needed, $120 might be a bargain.
At any rate, if you are going to light those speakers up to full power, I would make sure you replace the factory wiring eventually.
If you didn't agree on specifics of the job *up front* it is going to be hard to argue for the installer to do it for free. Maybe he will, maybe he won't.