Depending on the dealer or the region, it can be tough to wheel and deal on the price of a hot selling vehicle as some dealers are less inclined to negotiate. Part of the reason you're not seeing much in the way of discounts or incentives offered on the Grand Cherokee or even the Wranglers for that matter.
As some have mentioned, a low cost/low hassle way to pay a little below invoice is signing up for Treadlightly. It looks like the base membership where you get the Chrysler Affiliates discount increased to $100. The $100 is tax deductible and you don't have to go through any headaches trying to negotiate a fair price.