What is Jerusalem worth?

Jerusalem with it's castles, forts, bricks and mortars, gold and silver and silk and everything else of material value is considered to be devoid of any true value in the eyes of salahuddin. Hence he says 'nothing'.

Remember that Balian asks the question 'what is Jerusalem worth' in the context of being bewildered as to why Salahudding fought such a long and arduous war, which cost the lives of thousands of people, in order to capture the city? Balian is portrayed in the film as someone who does not entirely understand spirituality, hence he says 'God does not speak to me'. Therefore, Balian and Salahuddin are shown to be men who are driven by two completely different things; and Balian does not entirely understand Salahuddin.

So to negate any possible assumption Balian might have had in his mind, that salahuddin fought for some kind of material gain, salahuddin says jerusalem is worth nothing. But then he adds, that it is worth everything.

Now, something which only carries material value cannot logically be worth more than everything else. And by everything Salahudding literally means the entire world. Thus by making this statement, Salahudding makes it clear to Balian that the true value of Jerusalem stems from the fact that it has been exalted above all other places by God.