When people want a conclusion they can often find 'hard data' to support it. One by careful 'categorization' of data you can provide evidence that a project will pay off. If there's not enough immediate payoff, keep looking at secondary and tertiary 'benefits' until the numbers come out right.

I remember reading an article some time back about a city who wanted to justify promotion of an 'arts district'. They just included more and more of the area's commerce into the equation (as a benefit of the district) until they got the numbers they wanted. The fact that those benefits might not come from the project, or would come regardless of whether the project was implemented were conveniently ignored.