There are a good amount of cards to choose from, which range from Gaea's GiftGaea's Gift to Armor of ShadowsArmor of Shadows
Genesis Hydra would get as big as the amount of mana you had to cast it
This is in line with the ratios from Standard sets, but keep in mind that there are often special cases, like a Mystical Archive or a foil Phyrexian Vorinclex messing with our perceptions of scarcity
Whether these inflated prices will hold remains to be seen, but considering the events month-long duration and no indication from TPC or McDonalds that supply shortages are expected, its unlikely that these mark-ups will hold
Conversely, something like Ancient Copper Dragon is going to end up overshadowed by whatever giant fatties they print next year simply because they wont end up being $50
That means there are 99% more PSA 10s than BGS BL 10s