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 answer is two: Chalice of the Void from Mirrodin and Orochi Hatchery from Champions of Kamigawa
Chart shows the price of Annihilape [Holo] #109 at the end of each month going back as long as we have tracked the item.
Deconstruction I've used relatively simple examples thus far, but let's take the plunge and show you a very cool card with a lot of information about it and deconstruct what we've learned today
The bundle is on up for grabs for $44.99