Soumitra, the very function of a brand is to allow the observer to 'attach a value' to something. So if it's a Mercedes it is better than a Ford (even if you haven't actually SEEN either).
Unbranded pens (by which I think you mean not-so-well-known branded pens) are an unknown quantity on the vintage market, so they will have to be seen, handled, tested, examined before a value can be attached to them. First off this is difficult in the internet age, because most exchanges are virtual these days. Secondly, the vast majority of fountain pen aficionados are nowhere near as knowledgeable as they think the are - they will buy the 'brand' because that gives them the most kudos. "Look, I use a MontBlanc/Waterman/Montegrappa vintage pen - I MUST be an expert!"
So the short answer is Yes, our pens are not likely to top the list of vintage pens on offer when we are pushing up daisies UNLESS we manage to leverage our brand into something bigger a la Richard Binder or Edison Pens. But our pens can become cherished family heirlooms for generations to come.