And Crump too proved to be a basic duelist, starting with his Deck Master
The most important factors are edition (1st Edition, Shadowless, Unlimited), condition (mint cards command premiums), rarity (holographic, secret rare, full art), age (vintage Base Set cards are highly sought after), and the Pokemon itself (Charizard, Pikachu, and fan favorites are worth more)
The end results of these fusions is usually based on the type of Digimon used for the fusion
Even a PSA 10 card can be relatively inexpensive if its readily available and not in high demand
#26 Fatal Push 58.35 Description: A staple removal card in many formats
If you are willing to pay for the service, Beckett has been an industry standard for trading card valuation (well beyond just MTG) for generations