Inchoate text: please do not fork
Albert Einstein wrote "Not everything that counts can be counted, and not everything that can be counted counts." That might be paraphrased, perhaps less elegantly, as "Not everything that can be measured matters, and not everything that matters can be measured." Either way, this much seems undeniable. But _many_ things that count can be counted, and _many_ things that matter can be measured, and we have many reasons to do both.
**Measuring what has been saved**
For example, every time someone else performs an action that saves one of us money (which here means legal tender), should that not be recorded? That action will have had the same value (benefit) as a transfer of legal tender, so is it not equivalent in its value to us? Is the sum of legal tender saved not worth recording?
Whenever I receive something of value to me in a way that allows me to avoid spending legal tender, I can record that - and so can whoever provided that thing of value.
We both know that legal tender could have changed hands, so we can both agree, one way or another, what the price in legal tender would have been - and we can both record that. In this case, the exchange has been recorded in a form of money that is "metrically equivalent" (meaning the numbers or measures are the same) and in which we each hold an account. The fact that this has been accepted as settlement of this transaction is what makes this money - de facto money. It is not like legal tender, which has to be accepted as settlement if offered. No-one _has_ to accept such a community currency, but **anyone can choose to accept it in place of legal tender** - and at that point the immediate obligation has been settled _to the satisfaction of the two parties concerned in this transaction_ (the only two parties whose business it is with the inescapable exception of the tax authorities if the transaction is of a type that falls into their sphere of legitimate interest).
Such a payment involves a commitment do things for others, each involving an exchange the "value measure" of which is agreed in its own context. Over time, if the measure of what we each give and receive are not too far apart, we can feel confident that no one has just cause to doubt our value - whatever that is - to the community we share.
If, in our community, legal tender is too scarce to waste, we probably both know that. There are many things for which only legal tender will be accepted.
We will also both know that legal tender flows in, around, through and out. Therefore we can both see that what flows in, through and out is in some important way different from what flows around and within.
That may seem like rather a lot of a additional work for something that would probably have been done as a favour, but we all quickly lose track of how much we have done for others over the years. Altruism and eudemony arise in the here and now, not in deferred expectation.
In any case, the process can be smoothed, simplified and, increasingly, automated.