I'm pretty sure nobody cares if long-term players are quitting the game. Once you're at a certain level, buying stuff (except perhaps $3 a month for daily diamonds) hardly makes a difference. It's newer players that are buying these deals because a gold chest and 5 soulstones make a bit more of a difference at the beginning than it does at level 120.
GREE can be as greedy as they want to; I don't need their lousy deals in order to get lots of loot, gold, and XP. I just need patience.
You'll find the game a lot more enjoyable if you don't break the bank on it and instead develop a little patience when leveling heroes up. So, if you're a high-level player fed up with the game, quit I say. It'll be one less player I need to step over in the fight pit or coliseum.