Website development costs are notoriously difficult to estimate. Cost overruns usually result from unknowns inherent in the software development process or changing design specifications during development. Estimating development costs and then getting funds approved is an essential starting point. Websites are not created out of thin air. Whether a site is developed with a generous budget in a well-furnished studio or as an after-hours skunk-works project, it requires people, equipment, time, and materials. Your ability to accurately estimate the cost of these resources is crucial to your success in managing such a project. Cost estimates for websites that function as a marketing tool of an existing business are important. For dot-com businesses, where the website essentially is the business, estimates are crucial.

Like scheduling, cost operates in the dynamic of the three project management factors. Directly corresponding to resources, cost depends on time and task. A simple website (small task) will cost less (fewer resources) than a large, complex one. In order to develop an accurate cost estimate, the task and time available must be predetermined. This interrelationship among the dimensions is a primary cause of confusion in determining how much a project will cost. Without setting two of the parameters, the third cannot be accurately derived.