Cost for D train (10 hours from Beijing to Shanghai): 730 rmb for a soft sleeper (about 110 Australian dollar). you may search for the train schedule at China Trains(https://www.travelchinaguide.com/china-trains/)
As to the restaurants, it depends on what would you like to eat. Generally, you can eat fairly well at good resraurants with paying 100-200rmb per person.