IT exists to provide value, to participate in the achievement of organizational strategic goals. How can we prove we've done so? Just because we've built a thing, that doesn't mean much. Does the thing work? Does the thing provide value? Is that value measurable and consistent with the corporate mission?

Some quantifiable benefits of IT work can be improved operating efficiencies, enhanced personal productivity, enhanced decision quality, and/or enabling or supporting organizational strategic initiatives. What's most critical is to ensure the credibility of any measurements used to justify IT investments and provide after-the-fact valuations.
You may be working on a project that will reduce a process from five person-days' worth of work to two. Does that mean three people are going to be fired, with the resulting compensation cost saving attributable to your project? Probably not. Those folks will most likely be reassigned; so don't take credit for expense reductions that aren't going to happen.