As it should be. They cant deliver content if they cant pay employees to make it.
Guild Wars 2 and its predecessor was entirely free outside of the main game and purchase of expansion and had a pay to look awesome model, which worked for many years. DC Universe Onlie has pulled a simmilar model now and are still raking in money even though the monthly's aren't as high as the Premiums or the Freeloaders. (Premiums meant you spent money on the game and get more benefits than the freeloaders (a lot more), but not as much as subscribers do persay, which is just in game money, character slots, and inventory, plus vault access and que times)