I've got no reason to question his competence. Although I can't understand why he's only changing the friction plate after spending all day getting to into it. 'It looks alright' isn't a reason. It makes absolutely no sense unless to do that unless it's a job you haven't done before and haven't been bitten by that mistake yet.
It really isn't much more to buy the assembly. Most places sell it as a kit. And the bolts are single use too..
I was really only interested in the price to see where I sit in the market. I'm being nosey. But I obviously do appreciate that there are multiple factors when it comes to pricing up a job.