The price for Business Class ticket on the High-Speed Train Shanghai - Beijing is running at RMB 1748.
First Class is RMB 933 and Second Class is RMB 555.

Now, if I have a budget of RMB 1748, I rather take Air China or Eastern Airlines Business Class, which offer flatbed on their plenty widebody flights between Shanghai and Beijing. I usually pay around RMB 1300/1200 for flatbed Business Class.
Even if I am stuck on the tarmac for 4 hours due to the air traffic congestion, I can snooze in my flatbed. Moreover, I do not have to face the precarious taxi situation at Beijing South Railway Station