I’m not sure others will find this argument persuasive. But one argument for the morality of markets goes like this:
A. It is wrong to use something someone else values more.
B. But theft is also wrong, even if the thief values the object more than the current owner.
Prices give a signal that someone else values the item more, solving (partially) problem A.
And then the possibility of exchange means that markets can solve problem B, since there are bargains where both parties are better off, but the person who values the item more ends up with it.
A happy consequence of this system is that we can never run out of anything where property rights are specified clearly and prices are allowed to adjust to reflect scarcity and signal the fact that other people value an item more than the current owner.