To understand the history of TCG releases more clearly, you can also check out when did Pokemon cards come out for helpful context
It does not average out to a 7
I believe this back-and-forth between different teams is one of the things that helps us make richer and more integrated sets
Finisher spells and other wincons need a bunch of mana to get going, and reliable access to 10+ mana in the mid to late game becomes the goal, with many decks opting to aim higher if they can
Chameleon Blur: C Another four-mana fog, but it prevents all damage creatures would deal to players, not just combat damage, which is great, but still too expensive for my liking
TOP 20 ELVES IN MAGIC TIRELESS PROVISIONER Tireless Provisioner released in Modern Horizons 2 , a set which ended up with a number of banned cards due to sheer power level