Somebody has to pay for all this. Software development that doesn't acknowledge economics risks the hollow victory of a "technical success". Make sure what you are doing has business value, meets business goals, and serves business needs. For example, solving the highest priority business need first maximizes the value of the project.
Two aspects of economics that affect software development are the time value of money and the option value of systems and teams. The time value of money says that a dollar today is worth more than a dollar tomorrow. Software development is more valuable when it earns money sooner and spends money later. Incremental design explicitly defers design investment until the last responsible moment in an effort to spend money later. Pay-per-use provides a way of realizing revenue from features as soon as they are deployed.
Another source of economic value in software development is its value as options for the future. If I can redeploy my media scheduling program for a variety of scheduling-related tasks, it is much more valuable than if it can only be used for its originally intended purpose. All the practices are intended to enhance the option value of both the software and the team while keeping in mind the time value of money by not investing in speculative flexibility.