Describing our primitive ancestors, Robin Hanson writes,
when the group was stressed and threatened by dominators, outsiders, or famine, the collective view mattered less, and people reverted to more general Machiavellian social strategies. Then it mattered more who had what physical resources and strength, and what personal allies. People leaned toward projecting toughness instead of empathy. And they demanded stronger signals of loyalty, such as conformity, and were more willing to suspect people of disloyalty. Subgroups and non-conformity became more suspect, including subgroups that consistently argued together for unpopular positions.
I suppose that people see charging a high price for something in the wake of a hurricane as disloyal. The situation calls for group solidarity, and instead here is this merchant looking out for himself.