Yes, that does seem high, even for Alaska. Assuming $30/dinner and $15/breakfast, the total would come to $270. I suspect that there is some cruise line overhead factored in.
Is there any way you could visit Denali on your own? There is a wonderful restaurant in Healy (about 10-12 miles north of the park) called the Black Diamond Grill and it was listed on that Tripadvisor link Jackal gave you. You would gain flexibility with a car and hotel arrangements you make yourself.