I have some doubt about transportation between Shangrila and Kunming.

Actually, no train runs between Shangri-la and KM. Thus you have to take a train to Lijiang first and then transfer to a bus to reach KM.
There are direct buese between the two destinations. And if you wish to catch it, the night bus is suggested. After some time of sleep, you can get to your destination.
And for the airticket, its fare changes a lot and the discount also changes from time to time. So I suggest you search the website to get more information:
https://www.travelchinaguide.com/china-flights/