For us, vacations are an investment in our family unity. In that sense, they are "priceless". Depending on our financial situation (husband is in commissioned sales), we have splurged on some occasions and "tightened the belt" on others.
We have been known to let the big kids know our general plans and explain a "light" level of gift-giving for upcoming holidays and birthdays, do bday parties at home, recommend Disney giftcards when relatives or friends ask for gifting ideas (even for the grownups - us - LOL).
WDW has several money-saving strategies they offer, such YES tickets.
We just took our 2 youngest children for their 2nd birthdays last month. It was wonderful and manageable. Babies are up early anyway, so we hit rope drop and did the parks until lunch; went back to our unit, ate lunch and the little ones napped; then they snacked or had early dinner upon awaking and we headed back out to the park for the evening. Some nights they drifted to sleep in their stroller and we stayed a bit later doing "adult" rides. Other nights we headed back and had them in bed fairly early. We equipped our diaper bag with a huge variety of snacks, a few familiar toys and comfort items and a small portable DVD player which came in quite handy during a sitdown meal. They were mesmerized by the sights and sounds, loved the kiddie rides and were totally taken by the characters, dance parties, fireworks, parades and characters. They truly "behaved" for over 85% of the trip.
And the cost savings... hello??? The twins had free park entrance, ate for free off of our plates and off of their own at buffets and were showered with an immennse amount of birthday related pixie dust.
In 2012, we are taking all 5 children (at time of travel - 13,11,9 and 2 weeks shy of 3 for the little ones -free AGAIN). We are staying on property in a 4 bedroom/ 4 bathroom unit, utilizing our kitchen for most meals, doing 3 character buffets, bringing our own snacks, doing YES for our park tickets and driving down. Total cost is approximately $3100, including gas, and souvenir money. And that figure is for 7 nights.
Like I said, for us it is an investment. In memories, bonding, the fun of planning and anticipating. We enjoy the whole process.