If you can't get the discounted super rates at the value resorts, you can save a lot of $ by staying at one of the WDW properties on Hotel Blvd over by DD. I know that some people don't care for the Grosvenor, but it's one of my favorite places to stay if I need to save a few bucks, and still be close to the Disney action. I love being able to walk across the street in the evening to get an ice cream cone from Ghiradelli's. You can often get the Grosvenor for $89 on the internet. The Best Western right down that same block might even be a little cheaper.
And, depending on where you live in NJ, you might get a better air far rate in Phila than Newark. You could always drive from NJ (been there, done that...never again!)
You didn't mention if you have kids, or their ages, but I find that renting a small car is about the same price as hiring a car to get you to WDW from the airport. I'd never consider NOT having a car...it's just SO much more convenient. I've even found a car at L&M (they are located in the airport, right next to the Dollar counter) for $77 for a week! That is definitely the least expensive way to go.
Nw, of course if you really want the CHEAPEST way to get to WDW from the airport, take a public bus! You have to make a transfer and it takes about 1½ hours, but it's under $2!
On our last trip, we stayed for 16 days (splitting between offsite, Grosvenor and the then DL). We only had 7 day passes and found lots of other stuff to do for 9 days! Touring the resorts is a fun way to spend a day. Ride the monorail and ask to sit with the conductor! FUN way to ride, with a great view!