Symbolism, Imagery, Allegory
Dickens occasionally throws in a few criticisms of people like Julia Mills and the Waterbrooks, society types who think a lot about money and reputation and not very much about other people. But there is no greater symbolic showdown between the power of money and the power of personal feeling than in the cases of Mr. Micawber and Mr. Peggotty.
Both Mr. Micawber and Mr. Peggotty face this interesting crossroads where they are offered money in exchange for something of emotional or moral value. In Mr. Micawber's case, Uriah Heep assumes that Mr. Micawber will keep quiet about his plots against the Wickfields and David because Uriah Heep is paying Mr. Micawber a lot of money.
In Mr. Peggotty's case, Mrs. Steerforth explicitly offers him cash as a payoff because her son has abducted Mr. Peggotty's adopted daughter, Emily. And Mr. Peggotty also receives a couple of cash payments from Emily herself while she is on the road, as an apology for running away.
In both of these cases, Uriah Heep and Mrs. Steerforth are offering blood money – cash in exchange for letting the status quo stand. And both Mr. Micawber and Mr. Peggotty refuse: Mr. Micawber collects evidence to expose Uriah Heep to David, Miss Betsey, and Traddles. And Mr. Peggotty rejects Mrs. Steerforth's offer point blank and then holds onto little Emily's payments until she is found so that they can be returned to the Steerforth family.
These occasions both demonstrate in a nutshell the text's lesson about money: you can never allow it to dominate your moral choices. And the assumption that poor people will be ruled by money makes you look really bad.