Replica's have not historically, gone the heavy collertor's route but it's in the fledgling stages.
Rarer models ..and some now gone early manufacturer's are starting to see some interest and respectible prices paid.
Armi San Marco is now out of Business and the 18" Dragoon would qualify as a low volume manufactured model.
With the fact it is now out of Production and somewhat rare..there could be good interest.
Price is however hard to judge... Condition ( NIB or well used ) having much to do with the Price Range.
What with a Strong Euro vs the US Dollar...New in box current production of models will have an influence.
If your buying, or are you selling ..... the value is how badly you want it or how gadly you need to sell it
Sorry, to be vague...Pehaps someone can offer a current book on Blackpowder Arms values...