I've never bought from La Jolla but two things strike me as strange: (1) was the salesman specifically told the parts required were for a coupe? Why did he mistakenly think they were for a 2002, and (2) the “coupes are approaching $100,000 so parts should reflect that,” attitude. So what he's basically saying is that, since coupe prices may be going up, La Jolla will charge "what the traffic will bear". Personally, not the kind of establishment I'd like doing business with. Yes, I know, they all do it but it's much easier to swallow when it not thrown into the customers face.
You've no direct experience. Good of you to admit that so we can take the opinions in context.
Parts misidentification: humans make mistakes ... all the time. Famous folks have been say something to that effect for millenia. What counts is how people deal with mistakes they've made.
If coupes are going up in price, more of them will undergo restorations. That'll increase demand for parts and hence parts prices will go up. Look at what's happened to tool kits in the last 5 years, as an example. And, why wouldn't used parts reflect, to some degree, the value of the car they fit? If LaJolla over charges, they won't sell. And that's their decision to make.
Now, if LJ were a teeny place struggling to stay afloat, I could see them refusing to address their mistake by selling the parts at the lower price. But, I thought they were a pretty big vintage BMW shop, and if I were the owner ... I'd have bit the bullet and walked away from a few hundred bucks for the sake of not pissing off a customer (even if the customer were a bit unreasonable).
I've dealt with LJ on parts and have had 100% perfect service/attitude. THe guy who restored my previous E9 spent BIG $$ there and had only the best to say about LJ. The take away is that while LJ may occasionally screw up, and sometimes they don't take the high-road when they do, the vast majority of their customers are probably happy with them.
So what's left to argue about other than people telling each other how a 3rd party should run their business?