I’ve come to a point where I need to attempt a better distinction between price and value.
First, price is to money as length is to a ruler or duration is to a clock, that is it the actual number of the measure. Now as the Philosopher teaches, money is the measure of desire. Price then is the quantification of something in terms of how much of something else I must give up for it. Based on my desire for each, some transaction will occur in certain quantities.
In this sense, price is grounded in the subjective desire for something. In general, we desire things for what they are worth. I have a good estimation of the value of water and I desire it in the measure of its value to me and will pay a corresponding amount of money.
This brings us to value. Value is in a manner subjective, but fundamentally it is grounded in something objective in the thing. Whether we consider intrinsic, extrinsic, conventional or contextual value, it is grounded ultimately in the thing itself. It is the goodness of thing itself with respect to a rational creature with relevant needs.
Price becomes unhinged from reality when subjective valuations do not correspond to objective value. This can happen in any number of ways, but many will involve certain errors in knowledge concerning the object. Supposing a thing to possess properties does not or cannot possess may make it more subjectively desirable contrary to its objective value. Such a price can only be corrected by considering value as such, which involves the messy business of thinking about essence and ends.
A principle of just price then is that it corresponds to a thing’s real value. This is to say that a person’s desire for a thing is ordered by right reason with respect to the object or one possesses temperance.