These reasons include the card's rarity, popularity, age, and design
1 Foil-etched uncommon 1 Traditional foil rare or mythic rare 1 Non-foil or traditional foil extended-art rare or mythic rare Approximately 1 in 3 boosters contains a traditional foil extended-art rare or mythic rare
It should make the instants and sorceries deck better near the end of the game
Especially with third party resellers such as Magic Madhouse or TCGPlayer, the unregulated market can see massive overinflation spikes in the weeks following a new release
So far, the numbers on Iconic cards are fewer and farther between, and there havent been consistent enough results to know the percentages
For SWSH era, alt art is taken apart from full art V and full art trainer though they should all be printed on the same sheet