Creating an effective budget for your plumbing services is an indispensable step towards achieving and maintaining financial stability in your business. This process is not merely about crunching numbers or arriving at a rough estimate of expenses. It involves a thorough understanding of finance, an in-depth analysis of your business, and a strategic plan - all to optimize costs while providing quality services.

To begin, it is crucial to understand the economic principle of scarcity - the fundamental economic problem of having seemingly unlimited human wants in a world with limited resources. In the context of your plumbing business, your resources might include capital, labor, and time, while the wants could be your financial goals, client satisfaction, and business growth. Hence, budgeting helps you allocate your scarce resources efficiently to meet your needs.

The first step in the process is to identify and calculate your costs. Fixed costs, such as rent and insurance, remain constant regardless of the level of services provided. Variable costs, such as labor and material costs, change in direct proportion to the volume of services rendered. Exploring the law of demand may prove beneficial here. The law states that, all else equal, as the price of a product increases, the quantity demanded falls. In this context, it means that as the price of your plumbing services rises, the demand may decrease. Therefore, any increase in your costs should be carefully weighed against the potential effect on demand.

Once you have a clear picture of your costs, take a step towards understanding your revenues. The principle of marginal analysis is particularly useful here. In economics, the term 'marginal' refers to the next additional unit. By applying this principle, you can understand how much additional revenue the next job will bring in and compare it to the additional cost of performing that job. This will help you in pricing your services optimally.

Next, consider the time value of money, a fundamental principle in finance that suggests that money available today is worth more than the same amount in the future. This principle is due to the potential earning capacity of money, which could be lost over time. For instance, if you have upfront expenses for a job that will only pay upon completion, you are essentially providing an interest-free loan to your client. Therefore, it might be prudent to request a deposit or staged payments to align your cash inflow with your outflow.

Lastly, a budget should not be a static document. The principles of Bayesian inference can be applied here, which involves updating your initial belief based on new evidence. In the same way, as your business evolves and new financial information becomes available, adjusting your budget accordingly is vital.

In conclusion, budgeting is not merely a financial tool, but a strategic instrument that can enhance the viability and growth of your plumbing business. It is about making informed decisions, backed by key principles of economics and finance, and adjusting these decisions as your business environment changes. While this may seem complex, remember, as Gustave Flaubert said, "Pleasure is found first in anticipation, later in memory." The anticipation of a financially stable and growing business makes the effort worthwhile.