For me money is a token of trust. The value of it simply is a derivative of the trust.
So the more you trust your ten dollars, the more they can buy?
Isnt it self evident?
But on a serious note you dont trust the dollars they are the token of your trust to economy, society, that the commodities you buy are up to your expectation, your employers will do their job etc, or if you like that god will not end the world tomorow