Chinese did their study alright, and then only proposed $58 Billion bill constructing a railway line through Himalayas.
By all means construct a single railway line that costs two times the entire annual federal budget of Pakistan, but don't ever believe, that you will be able recuperate that amount by transiting goods to china.
Here is for context, constructing a 1000 km strech for a normal broad gauge railway line, costs about $1 billion.
Here you will be spending approx $ 50 billion for constructing just a 100 km strech of railway track through Himalayas.