I'm assuming you won't have your own car in Denali. This will limit your options, as some of the better restaurants (and better prices) are outside of the Glitter Gulch area where the cruise line-operated resorts are.

If you will have access to your own transportation, there are some good options about 15-20 minutes south of Denali (McKinley Creekside Cafe, 229 Parks [more expensive but very good]) and 15-20 minutes north of Denali (the Healy area). Otherwise, you're largely limited to the restaurants attached to the cruise line resorts and the lone outpost of Franchised America™: Subway. I would think you could do better than $30 per meal, though.

Can't speak to specific costs, but you might have luck reviewing the (limited) restaurant listings around Denali and possibly Googling them for their web sites and menus: http://www.tripadvisor.com/Restauran...ve_Alaska.html

You mentioned "other parks": if you're talking about Kenai Fjords and you're staying in Seward, that's a real town with real restaurants. Prices are a little higher than Lower 48 prices but aren't insane. Otherwise, what "other parks" are you referring to? Alaska is huge, and some parks are in extremely remote areas where there aren't a lot of people and consequently not a lot of eating options.