Don't think we got a discount, but we did get last minute rooms back in August of 2003 ... had planned to stay offsite, got into that hotel at 1:30 AM and it was BAD!!

I was on the phone to Disney CRO as soon as they opened ... I think I was a bit hysterical

- but I do remember asking if they had any rooms for under $100 per night ... anyway the cast member was very nice and got us adjoining rooms at ASMo (actually, she gave us our choice of All Star resorts) at a rate of $99 each per night. At the time, it seemed very reasonable, all things considered.
Would I try that again ... nope, now we just book onsite as soon as we decide to go ... better to have a Disney room at "rack rate" than be forced to be offsite.