Cost variances on projects come from a variety of sources. Here's a picture of some of the drivers that are common in many domains.
- Where are we going?
- How do we get there?
- What resources are needed?
- What impediments will be encountered?
- How is progress to plan measured?
These impacts on cost variance are part of principle 1, 2, 3, 4, and 5. They are part of all the principles, because without a credible understanding what the project is going to cost in the end, the management processes of the project itself are no longer credible. You're then just spending other peoples money with no connection to producing value - yes the business value.