Agreed, things are valuable because of our subjective view and many times this depends on what we can do with them, a perfect and modern example of this was oil, for thousands of years farmers excavated in order to try to find underground water and cursed their luck when they found oil, why? Because we could do nothing with it and as such it was not valuable, but then we learned how to do something with it and farmers went from cursing their luck to dance in happiness when they found oil.

Another good example of subjective value and how it changes depending on our circumstances is a bottle of water and 10k dollars in a bank account, a bottle of water is not very valuable if you are in a city and the 10k dollars will be of more use in those circumstances, but if you are lost in the desert then the value of that bottle of water increases dramatically while the 10k dollars in your bank account become useless during those circumstances.