Abhi-
http://www.swisstravelsystem.ch/en/s...l-system/news/
You have probably already seen this link. Featured rates are usually discounted.
I've travelled this route a few times, and the ascent / descent is steep and scenic. I've also driven in ( Lugano-Menaggio-Maloja-St. Moritz-Sondrio-return) and the train journey is far better: Less obstacles to worry about, and much more scenic.
On the subject of altitude gain, some of our guests have experienced a touch of altitude sickness on excursions to the higher mountains. A small investment in tablets for Seasickness (containing Scopalamine ) to your travel First-Aid kit might be a very good idea.