We go a lot, it's quite the joke with our friends. Here's how we manage (on one rather modest income too)
AP's: We usually take at least one long (2 week) trip and several short trips during the year. alternating our long trips: August the first year, June the next in order to get two "big" visits on one AP. The other trips are usually one just the kids and me and one just DH and me. (Isn't it a coincidence that that me just keeps cropping up?) It usually amounts to about 35-40 days on one PAP.
We Camp: For the long trip we always bring our "vintage" Airstream trailer (purchased 10 years ago for $2000). With discounts, a premium campsite runs around $45/night even in the summer. When just the kids and I go I get the best discounts I can. This year it's the $49 rate at the All Star Music. I have done Priceline and gotten the Wyndham for the same amount at Easter.
We Rarely Eat Out: I think this factor alone is a budget buster for most families. Since I cook, freeze and bring in 90% of the food we eat, the expense over eating at home is practically zero. I have brought in hot pots, hot plates, crockpots and even a microwave when we don't have the trailer. I just purchased an electric cooler since the Disney fridges have gotten so expensive and we bring one ice chest for drinks, milk and stuff. I used to freeze a case of water bottles to keep the food cool. This works very well. At Easter we still had frozen bottles after a week. We usually have one "nice" meal out. This August it will be Boma.
I Don't Pay for Souvenirs: We have teens and they have to pay for any extras. DD usually buys a souvenir, DS blows his on junk food. When they were younger they received Disney Dollars as gifts or rewards and used these for their purchases. I know a lot of people think Disney Dollars are a rip-off but they're great for setting limits with young ones.
We Drive: As you may have guessed from all the stuff I bring. It's about 10 hours for us. DH and I will be flying in September on a Southwest special ($179 round trip for both of us) so this will be quite a treat.
I know everyone can't pull all of this off due to distance or lack of vacation time, but it can be done. We went to Disney's Magic Music Days with my daughter's dance team a couple of years back and everyone with us spent more in 5 days than we did in two weeks and kept wondering that we could afford such an "expensive" vacation so often! The difference? No discounts on tickets or hotels, airfare, and dining out at every meal.