I think this has been handled badly—not the pricing or the content; Anet is free to do as they wish there—but psychologically. Originally you bought the game and got content for free. Now you buy content and get the game for free. It’s a confusing reversal of the business model.
This is what they should have done (without changing anything, really), but it’s too late now:
1. Called it Guild Wars 2.5. No-one would have been irritated with the price or the fact that the old game came included.
2. Put the expansion into 1 out of every 1000 black lion chests and said so publicly. Players would have bought chests like mad, and every time someone reported winning one in the chat, more chests would have been bought.
But disregarding bad marketing strategy, at least it isn’t Sims.