Each system is unique. However, by capitalizing on similarities we can reduce the time, effort, and cost for some or all of them, and thus the quest … - Harold Chestnut

System costs can be considered in many different ways. For example, the cost for making the system and the cost for operating it may be used as a basic for judging the total cost. The total cost may also be arrived at in another fashion, as, for example, the sum of the fixed cost, variable cost, past investment and other charges. Furthermore, in many cases where systems engineering is required several time phases are involved for which the cost factors may be significant, such as the study phase, the breadboard phase, the prototype phase, and the production phase.

The Systems engineering method recognizes each system is an integrated whole even though composed of diverse, specialized structures and sub-functions. It further recognizes that any system has a number of objectives and that the balance between them may differ widely from system to system. The methods seek to optimize the overall system functions according to the weighted objectives and to achieve maximum compatibility of its parts.

A model may be pictorial, descriptive, qualitative, or generally approximate in nature, or it may be mathematical and quantitative in nature and reasonably precise.