If I recall they do this pretty much every year, be it a CM or AP discount and its always at the holiday time.
I remember a while back (10 years ago) the holiday CM discount was 50% off.
When the margins are as high as they are for the prices they charge, they can still make a lot at 30% off.
That being said, being at the parks this week, the pricing seems all over the place. You will see a sweater that is 45 dollars and another sweater of the same style/material but with a different graphic on it but it's 65 dollars. I don't get it.
I am pleasantly surprised that most merchandise seemed cheaper than Disneyland though overall.