Retrospective Pricing: discovering price through an epistemic approach within ecological boundaries

Most exchange asks for price to be agreed before value is created, so price is set as a forecast and protected by margins against what cannot yet be known. This paper proposes Retrospective Pricing, a mechanism that treats price as a measurement. Before each 28-day cycle a draft cost and margin are published as a hypothesis. After the cycle, observed cost is measured and the difference is settled in the open among the participants by rules agreed in advance. The fair price is the household's only financial exposure, and hindsight can lower it but never raise it. Margin is held in cyclical, seasonal and annual layers matched to the horizon at which costs become observable, and surplus is distributed half to Nature first, a quarter to households and a quarter to the people who do the work. The mechanism holds only under stated preconditions: need disclosed before supply is committed, symmetric information, and ownership and governance closed by structure. The paper places the mechanism among nine neighbouring traditions, from cost-plus contracting to utility ratemaking and parimutuel pooling, identifies recurring, collated disclosed need as the element that, in combination with the others, distinguishes it, and works a full cycle through modelled numbers for a closed loop of household goods. Limitations, including the absence of observed data, are stated.