Money is the driving force Moll Flanders – both the book and the character. It's way more important than class, love, or anything else. Moll needs money in order to achieve freedom from the servant life, and once freedom has been achieved, she needs money to support that freedom, let alone enjoy it. Money is what pushes Moll to make all of her decisions, good and bad. Whether it's yet embarking on another marriage, sending her kids away, or turning to petty crime for a source of income, it's always the dough she's after. But because she's a woman, there aren't many options for getting ahold of some cash, so Moll has to resort to methods that are, well, not exactly above board.
Since money is motivator-numero-uno for everyone in Moll's society, the book continually reminds us of how unjust it is that there are so few legal ways to make a fortune.
By rewarding Moll with so much money after her career of illegal activity, the book suggests that succeeding financially has little do to with behaving morally.