Not sure about your prices.
I just checked (dates about a month out) and found on elong.com (switch to inglish in the pull down menue on the top right)
SZX-PVG 420 + 190 Yuan
PVG-PEK 570 + 190 Yuan
PEK-SZX 1030 + 190 Yuan
This was just for random days. You most likely can find something better playing with the dates.
You also can use the train between Beijing and Shanghai.