Are you sure you asked the same train No in the railway station as you see on this website? As far as I know, the price was calculated according to a fixed formula offered by the China Railway Bureau,there must be small differences, but cann't be 75% higher, unless the train was changed from a non air-conditioned into air-conditioned.
Also, you should know that train schedule may change from time to time, even the official website didn't show some of the changes, you can't ask this site too much for 100% accuracy.
Anyway, I hope this train search can improve little by little in the future.