The cost of a houseplant will range anywhere from a few hundred dollars to over a million dollars. Yes, a million. However, why are those houseplants so costly? Rarity, beauty, breeding, and proliferation are all factors that play a part.In recent decades gardening activity with the younger generations has become increasingly fashionable, and a “plant boom” is taking place later. So, naturally, there is also a rise to own uncommon and beautiful is sold at a three-figure rate.