For my last trip:
Airfare was about $250 roundtrip from Denver
Hotel and tickets for two was $1400 ($700ish for my half, 5 days in park & 6 days at the hotel)
Add an additional $35 for a shuttle to and from the airport
Looking at around $1250 just for my share of the trip itself.
Per day my spending was on average:
$5-6 at the hotel or McDonalds for breakfast
$10-15 for lunch in the parks
$3-4 for a snack or drink at some point
$10-15 for dinner in the parks
Depending on if I buy souvenirs or not, I can easily make it through a day spending less than $100 on myself. Heck, I could probably get by spending less than $50 if I had to.
Usually I splurge once during the trip and have lunch at a sit-down restaurant like Blue Bayou or Cafe Orleans, so that's an extra $30-40 that I saved up on purpose.
I also pack granola bars into my luggage so I have something to snack on in the mornings before lunch. Saves me some money on snacks. I'm still trying to figure out a way to bring my own bottles of water but I haven't quite figured that out yet.