The most telling M10 card would've been BSA you are right and that got reprinted. The huge outcry for Mythic raising prices wasn't really until M10 with BSA and then continued form there.
I think the problem with mythics all started with BSA, which is a groundbreaking game finisher at 5 mana and suddenly any deck that can afford to pay for the 2 white mana finds that they need BSA to compete. At the mythic rarity there simply wasn't enough to go around. M10 boxes are opened like crazy and sales were brisk.
Every set since then includes at least a mythic that tries to replicate that BSA factor: insane ability that can be used by any deck with a splash of that color. Had BSA been a more logical WWWW1, things might have worked out differently.
I think the problem with mythics all started with BSA, which is a groundbreaking game finisher at 5 mana and suddenly any deck that can afford to pay for the 2 white mana finds that they need BSA to compete. At the mythic rarity there simply wasn't enough to go around. M10 boxes are opened like crazy and sales were brisk.
Every set since then includes at least a mythic that tries to replicate that BSA factor: insane ability that can be used by any deck with a splash of that color. Had BSA been a more logical WWWW1, things might have worked out differently.