The first time you conceive a system based on a requirement, estimating the costs and benefits might be difficult. But, after implementation, you will have a much better idea of the costs and benefits triggered by that requirement.

A well-formulated, measurable, reusable requirement – including a full cost-benefit analysis as part of its description – is every bit as valuable as a reusable software module.

– John Favaro, “Managing Requirements for Business Value”, IEEE Software, vol. 19, no. 2, Mar/Apr 2002, pp. 15-17