Legal Eagle tells us the law:
… the essence of a penalty is where it imposes a payment of money in terrorem of the offending party (i.e. intended to frighten or intimidate); whereas the essence of a true liquidated damages clause is that it represents a genuine agreed pre-estimate of losses which may result from the breach.
Okay – but the issue is, how do we know what the losses are? So in comments Jarrah says that the courts do this every day. Indeed the courts do something but I’m not convinced they assess ‘losses’.
Attempts to establish cost accounts on an “impartial” basis are doomed to failure. Calculating costs is a mental tool of action, the purposive design to make the best of the available means for an improvement of future conditions. It is necessarily volitional, not factual. In the hands of an indifferent umpire it changes its character entirely. The umpire does not look forward to the future. He looks backward to the dead past and to rigid rules which are useless for real life and action. He does not anticipate changes. He is unwittingly guided by the prepossession that the evenly rotating economy is the normal and most desirable state of human affairs. Profits do not fit into his scheme. He has a confused idea about a “fair” rate of profit or a “fair” return on capital invested. However, there are no such things.
Then there is this (pg 332):
In view of popular errors it is expedient to emphasize that catallactics deals with the real prices as they are paid in definite transactions and not with imaginary prices. The concept of final prices is merely a mental tool for the grasp of a particular problem, the emergence of entrepreneurial profit and loss. The concept of a “just” or “fair” price is devoid of any scientific meaning; it is a disguise for wishes, a striving for a state of affairs different from reality. Market prices are entirely determined by the value judgments of men as they really act.
If von Mises isn’t to your liking here is James Buchanan:
1. Most importantly, cost must be borne exclusively by the decision-maker; it is not possible for cost to be shifted to or imposed on others.
2. Cost is subjective; it exists in the mind of the decision-maker and nowhere else.
3. Cost is based on anticipations; it is necessarily a forward-looking or ex ante concept.
4. Cost can never be realized because of the fact of choice itself: that which is given up cannot be enjoyed.
5. Cost cannot be measured by someone other than the decision-maker because there is no way that subjective experience can be directly observed.
6. Finally, cost can be dated at the moment of decision or choice.
What courts do is cost-accounting but that is something very different to evaluating the costs that people face when making choices.