The problem of moral sensibility as a source for political preference is widely discussed. This paper presents a parametric model for comparing differences in a particularly salient moral conception: the importance of disparity or inequality in bargaining position as a source of motivations to regulate exchange. Economists have assumed that "voluntary" exchanges are the norm, but this view is widely disputed. Our conception of "voluntary" exchange allows for a problematized view of alternatives, and we are able to offer implications of this theory for the actions of moral agents in a commercial setting. Not least, this approach gives analytical purchase on the question of when "voluntary" exchanges might nonetheless legitimately be regulated by political authorities.