Like most Pokmon cards, the value of Paras depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Aquapolis)
Plus WotC keeps printing cards that do the modular thing anyway like Dockworker Drone and Sin, Unending Cataclysm
They may be made of cheaper materials and may not be printed with the same level of detail as an original card
For the longest time, black card draw was always rare, but this was apparently safe enough to put into common
Cardboard residue (fluff) around the edges
Cards like Rule of Law, Archon of Emeria, and Eidolon of Rhetoric make it easier to keep your werewolves in their more powerful form