I think you can take a overnight bullet train from Shanghai to Beijing to visit the well-known Badaling Great Wall. The train ticket is CNY730 for first class and CNY327 for second class. I think about CNY1000 are enough for such a tour if you take the second class seat, including the transport fee to Badaling and then entrance fee. It's possible to take a overnight train back to Shanghai on the same day, if you will just visit the great wall.