Which incident are you talking about? There are a number of economies in the fictional town (and county) in Harper Lee's novel To Kill a Mockingbird. Let us know what incident you mean and you'll get some good answers, I'll bet. This novel is full of material for discussion.
The non-monetary payments from Mr. Cunningham to Atticus Finch tell something about the economy in Maycomb, for example. In the Depression era, money was hard to come by, and in this largely agrarian region in Lee's novel, the farmer pays his lawyer not in cash but in firewood and turnip greens.
Not everyone is poor, of course, and some people still have money to buy luxuries. There's a brief reference to out-of-town travelling salesmen (selling furs) in one place in the novel.
In the story "To Kill a Mockingbird" by Harper Lee the setting is the south. It is set during the time of deep financial depression in the south. Small towns often consisted of mostly agrarian employment. For white farmers making a living was a struggle, but for black men it was even harder. The south was not yet recovered from the release of slaves. Slavery had left black people uneducated and dependent upon white people for employment. The jobs open to them were limited and mostly included work as laborers, field hands, and domestics. There was a strong competition and resentment by uneducated white people over jobs. The jobs were often given to the white people first with the exception of being a household domestic.
In the book the reader is introduced to characters who are poor. Tom Robinson, the black man on trial, can not find work except for odd jobs. If he had been able to make money elsewhere he would not have been in the area for Miss Ewelle to kiss him. The two farmers are also poor Mr. Ewell and Mr. Cunningham. Yet they respond differently to their poverty. The resistance and competition of the poor white men who compete with income in the community against black men is brought to light in the story as part of the prejudice of the men.