What is the meaningful difference between the two scenarios?
Within the boundaries of the formal structure you’ve given the difference between blackmail and acceptable negotiation practice is largely a matter of social norms (and the usual complicated mess of framing games, preferences and status). We have no rule that people must sell or buy at the worst possible price that is still positive to them (in my culture at least, there are exceptions). We do have a (justifiable) instinct that revealing shameful secrets about people is an act of aggression and we are inclined to consider aggressive acts made conditional on something else that is not itself aggression to be ‘blackmail’ or ‘extortion’.
That description is supported in my mind somewhat by the observation that people consider things to be blackmail/extortion/threats even when they are mere descriptions of a Best Alternative to Negotiated Agreement. To my best approximation, for most people the evaluation of whether X is bad dominates the formal structure, rather than merely resolving between formally equivalent cases.
Within the boundaries of the formal structure you’ve given the difference between blackmail and acceptable negotiation practice is largely a matter of social norms (and the usual complicated mess of framing games, preferences and status). We have no rule that people must sell or buy at the worst possible price that is still positive to them (in my culture at least, there are exceptions). We do have a (justifiable) instinct that revealing shameful secrets about people is an act of aggression and we are inclined to consider aggressive acts made conditional on something else that is not itself aggression to be ‘blackmail’ or ‘extortion’.
That description is supported in my mind somewhat by the observation that people consider things to be blackmail/extortion/threats even when they are mere descriptions of a Best Alternative to Negotiated Agreement. To my best approximation, for most people the evaluation of whether X is bad dominates the formal structure, rather than merely resolving between formally equivalent cases.