Seems like the issue is you need to make $40 and pony up to the table. I mean you clearly like the game and want to continue playing it, just get the taken king and call it a day. But you should know that this isn't a trend that's going to end. Every new DLC and expansion is going to cost money and inevitably lock you out of content if you don't buy it. If it is that much of an issue for you, maybe it's time to cut your losses and pick a new game. As far as the legality goes it's perfectly legal. You agree to the terms of service. You're an end user, meaning they own the game and let you play it.