If you buy a sleeper from Chengdu to Urumqi, you can only buy a sleeper in Turpan, and you will pay for the ticket at the next stop. How to charge for sleeping berth? Is it the price difference between the sleeper from Chengdu to Urumqi and the sleeper from Chengdu to Turpan (this is the most cost-effective), or the price of the sleeper from Turpan to Urumqi (this is much more expensive, I would rather make it a hard seat)