Yes, it's a stupid question, and I know that the answer depends more on frame construction and materials than design. What I'm really asking is: All other things being equal (including construction materials, etc.) does adding the third wheel of a trike with its attendant frame members and axle increase the total bike weight by more or less than 33%?
Secondary question: Does the addition of the extra weight of a trike add anything to the bike other than stability at stop and during turns? It seems to me (looking at the available models on the market), that the rider's weight is much lower on a trike than on even a long-wheel-base bike. Does this really matter?