A lot of that 300 APM is from the early stages of the game where people are spamming actions like crazy. As the game goes on the average tends to come down. I do envy the players that are able to maintain 220+ in big battles though, but I only envy them if they're microing well and queueing units at the same time.
Actually no, the beginning APM isn't long enough to have a lasting impact on the next 30 minutes of the game. I have around 250 constant, no spam. Once you master hotkeys and mechanics it's second nature.
It's like how when we see a piano player playing at like 500 APM. She can just hit the chords and it will still sound beautiful. That's not the point though. While you can still execute strategy at a lower APM, that extra APM helps to execute it on a new level.
