At "AskAboutProjects" a user asked whether it's still Project Management when you aren't managing the budget. Mainly he answers floated around the point taht yes, it is. A few examples were mentioned inlcuding projects with a flat resource profile.
Here's the thing; Just because there isn;t anything to do on the budgets doesn;t mean that you are not managing cost. If your team burn through $20k per month, you have a pretty direct influence on the budget by the way you manage the project.
Will it go for 6 months or two years?
Of course cost is one half of the value equation, but it isn't as simple as a financial estimate or report.