While I'm sure it is a factor, I highly doubt it is responsible for all lost subs of this game, and all the lost subs of WoW.
Regardless of how broke we are, we will find a way to pay for what we enjoy. Even more so in times of stress. Whether it be a 9 dollar box of cigarettes, that number 9 at burger king, or a monthly subscription of an MMO.
Also, remember that the average person does not know how to manage their money correctly.
You'd be surprised how many people will say "I'll put that on my credit card" before they say, "I can't afford this right now."