>...When there is only one buyer or seller in any other case, we call it price gouging or price fixing.
Having one buyer or seller of a product or service is neither called "price gouging" or "price fixing".
>...Additionally, the "extra profits" or savings (in some cases) actually do contribute to maximum satisfaction of consumers.
There is really no evidence of that. (The basic concept of rent seeking is covered in any econ101 micro textbook.)
>...For example, if the only dealers were run by manufacturers then they could unilaterally decide that cars over 5 years old will never be repurchased, dooming those deals to private transactions with zero warranty, or else second-tier used-only retailers.
What a strange idea.
>...Again, appeals to authority do nothing for me.
No, that wasn't an appeal to authority.