Unless you are planning on driving to WDW anyway I would definitly stay on site at one of the values and that way you dont have to worry about transportation (as in car rental/fuel, parking etc)
Another way to really cut costs is to bring your own breakfast and lunch foods... (pop tarts, cereal etc for BF, the microwaveable pastas you can just throw in micro at the resort dining area , your own soda, water etc. The tuna and cracker packets you can buy are also great for a quick lunch.Peanut Butter and Jelly if you like it, anything that doesnt need refrigerated and there are a lot of options out there) and then eat counter services for dinner which you can find for less than $10. )
Anytime anyone tells me how expensive it is to go to Disney I have to disagree, it is all in what your "tastes" can settle for. If you are the type that has to eat out for all 3 meals, or has to have a snack at every snack booth, or a 3 course meal for dinner, and a lot of souvenirs then yes, Disney can be expensive, but there are many ways to be frugal at Disney without giving up the magic