Well, the earnings are based on playing 2 accounts. (1 level 5 and 1 level 3 Golden). They also include all possible ways to earn from the game (aside from tournaments that I never really play). Daily quests, season rewards, DEC earnings, blogging earnings, SPT, Monstermarket cashback, affiliates. If you are consistent in your approach and add benefit from all the small earnings it really does add all up.
Thanks