I just did this in May, and I do think there was a little bit of a discount - not much though. I bought a four day pass, and it was around $55 for a double stroller.
I remember thinking afterwards because we are going back in October that I should have bought the 10 day pass and had that cost out of the way and saved a little more.
But again, we're talking not much savings - but it is way more convenient than standing in those long lines.