I ride regularly. It sort of depends on what you want to eat. Lounge car has snacks and smaller items. Snacks were like the $3-5 range. Foodstuffs like hotdog/pizza/cheeseburger etc were like $6-8. Dining car food was more because you can only get full meals. Kids meals mostly about $8, adult meals depended on meal period. Breakfast $9-14, lunch $13-16, and dinner $17-30. That's all just rough ranges. I couldn't find current menu pictures either.
The train is referred to by the name Empire Builder. A quick check on internet produced no current menus. My recollection from my own travels on this train ~5 times in past 10 years, is that the snack bar prices are comparable to fast food burger and sandwich joints. The dining car (white table cloth, reservation req'd) is priced like a $$ restaurant. Time permitting, perhaps a call to Amtrak would give you more concrete data. Ciao.
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