I think the big disagreement here is on what people believe is satisfactory customer service. I would have been satisfied with the way this transaction went overall, and a $35 hold on my account for a week or so while the wrong mounting arm went back to BRS wouldn't have made me dissatisfied.
I also don't think it's fair to make judgements based on the purchase price or values of the items in question. From an accounting perspective, it doesn't matter if it's a $35 light mount or a $600 lawn mower. If you send out a replacement part for free, whether it's to replace a mistake or to replace a faulty part, you now have a hole in your balance sheet. If you don't receive the defective/wrong part back from the customer, you can't return it to the manufacturer or put it back in inventory (respectively). You're going to eat those costs and take a loss. I wouldn't do things the way you advocate if I ran my own business. Not by default. If a customer complained, I might see if we can make an exception. But, from the sound of things, you never complained about this at the time, so BRS probably thought this resolution was totally acceptable to you. Maybe I'm interpreting the transaction wrong, but from the way you described it, it sounds like this is the case.
Sure, maybe it would have been nice if they acknowledged that you spent $2k and paid for the part in transit for you, but they didn't. They DID gave you the $35 back after you sent the old one back and you have the light bracket you wanted in the first place. It was a hassle, but everything in life is a hassle, especially when things go wrong. Plus, at the end of the day you got what you want and were only inconvenienced by not having the mounting arm and missing $35 from your checking account for a few days. This doesn't sound like poor customer service to me.