In 2010 I and my friends climbed Muztagh ata.We had a good time there.I used his service last year and I didn`t have any problems. Price was as big as in other agency. I have to say thet his service was on high level but prices in China are really expensive - for service. I didn`t have any problems with extra expenses - we had just gentlemen agrrement.
I think that if you are looking for better price you have to join to bigger team. All organizators cooperate and they will try to join you.