^^Actually, I don't think cost of living has anything to do with amusement park pricing. Cost of living indices are usually reserved for, well, the cost to live or said another way, the necessities in life.
Amusement price points do not fall into that category in my opinion. In that case it is just good old fashioned economics. What will someone be willing to pay for what they receive in return? If the attendance data doesn't suggest a pricing problem, then why would they change it?
On a purely subjective note, I'm not so sure that the increased gas prices will have that much of an effect on leisurely travel this summer. We have been talking about fuel economy since 2001 (and before I'm sure) and I don't see much of a change in general behavior. Again, purely subjective reasoning based on the number of SUVs I see on the road and the fact that nowadays many do not appear to make behavior changes for fiscal reasons. They just go further into debt.
But regardless, doesn't the gas challenge just provide another opportunity for creative marketing and services? "The first 50 guests through the gate get a free gas card." "We now offer free shuttle service to and from the surrounding communities."