Meals in National Parks
You pretty much have 2 choice is national parks and most monuments: bring your own food into the park, or buy the immensely overpriced, so-so food they sell. Obviously, given the high cost and medicore quality of park food, I recommend bringing your own food in.A ham and cheese sandwich that you can make for $1, sells for 12.95 in Yellowstone at Old Faithful, as of August 2021. Basically, in Yellowstone even a very simple boxed, carry-out lunch with a drink (like water) cost an average of $18 (including tax) per person.
So, bring a cooler with ice, ham, cheese, peanut butter, jelly, water and drinks or whatever your preferences are and have lunch by your car... or picnic by a stream, waterfall, or geyser. We did that while watching Old Faithful for the 3rd time, and people walking by commented what a great idea that was!