Part of this is due to art and other concerns, but a large portion of the value comes from the fact that owning a first-edition foil of a valuable card is just very cool
Mid-Range Investment ($200-$1000): PSA 9 popular vintage holos, PSA 10 modern chase cards, BGS 9.5 premium cards
What about awesome novelty cards from tournaments and events
The answer will be trivial, but it does not lose its relevance
About EX Dragon Frontiers: Released October 2006, Dragon Frontiers introduced (Delta Species) Pokmon cards featuring Pokmon with non-standard types, like a Fire-type Mewtwo or a Lightning-type Charizard
Sure, you could just put Celebi ex straight into the Active on turn one but, with a relatively low health pool and the possibility of missing damage, Dhelmise is a much safer option, especially because your opponent will only take one point for a KO