Information technology (IT) costs often exceed budgets. Causes of incorrect IT cost estimation may either be suboptimal use of the knowledge on cost behavior or the appearance of unexpected situations. We develop a dynamic model that allows IT managers to test every possible scenario concerning cost occurrences. Users of the model would customize their inputs into the model to observe possible cost patterns. When the IT managers obtain a stable boundary of costs for their company’s IT portfolio, they will be more confident of their control over IT costs.