I had not heard this notion that doctors should project a monastic, self-effacing image to downplay their relative economic advantage lest their hickish patients risk their own health in a fit of envious rebellion against the doc's advice.
I mean, the white coat/scrubs dress code is good for obscuring finery, but people know doctors make money -- the secret is out. I don't think it is problematic, because most people want to go see the successful doctor, and they expect that their doctor is a high achiever.
I think obsessing on the accessories for 45 minutes is unprofessional, and that the interviewer perhaps let his/her personal feelings get in the way of conducting a serious interview.
And unless OP specified his pen, then it could have cost as little as $100. Just as there are watch nerds, apparently, there are ink pen nerds, and Montblanc has innumerable products ranging from $100 or so up to infinity. So just seeing the snowy crest shouldn't exactly trigger a Bernie-esque rage fit.