What is the cheapest way to be in kashgar from Pakistan .

There is an international long-distance bus from Pakistan to kashgar Xinjiang through Sino-Pakistan Highway. You can try to take it. Or you can take the direct plane by China Southern Airlines from Islamabad to Urumqi, Xinjiang, then fly from Urumqi to your destination. The best way for you is to take plane from Beijing or Shanghai to get there since it is very far between them. For details, you can check the China Air Schedule on this website.