Final answer:
In the story 'The Sky is Gray', it's unclear why the mother would pay without buying something without further context; it could reveal character traits or societal norms.
Step-by-step explanation:
"The Sky is Gray" is a short story by Ernest J. Gaines. Without context, it's difficult to provide a concrete reason why the mother would pay in 'the cage'—which likely refers to a cashier's area—without buying something in the hardware store. One can speculate that it might be highlighting an aspect of her character or a point of the plot. Perhaps the act demonstrates honesty, accountability, or it may be part of societal expectations or norms of the setting within the story. Without the specific context from the text, an accurate interpretation isn't possible.