Back in Cata I believe my old Realm CrushRidge fell apart and went from a high population realm to a low. A lot has changed since in that realms don't matter too much, though obviously they still matter. Blizzards devs put so much effort to make realms kinda unified but are hesitant to just give away free realm transfers.
Again, it's hurting the game. This is why making a character on a low population realm is a big no no, cause you're just screwing yourself. Which for new players, low population realms are the default. So once you level up your character, you're kinda screwed. Some experienced players wouldn't mind going to low pop realms as well. Some wouldn't mind going to PVE realms, or some would rather be in PvP realms. It's not like the game is healthy with 3.2 million active subscriptions right now.
It's time to let go of the greed Blizzard, and make a better game. Really should be focused on a good game first, and the money will always follow.