Amazon is the elderly gatekeeper of Skypiea. She lets people in even if they can’t pay her exorbitant toll, but purposely fails to tell those that don’t pay about the consequences for entering the city.

Mostly she seems to care about nothing. She explains to the Straw Hats, she is not a warrior and if they refused to pay the toll she would not try to stop them from entering. Her calm demeanor remained even when she found herself flooded with people fleeing to the Blue Sea in a panic. While she did not refuse to answer the Straw Hats questions, she neglected to them vital information about Skypiea’s currency Extol or the price of not paying the toll to enter.

(Source: One Piecce Wiki)