One thing is certain
You must know what all the project budget covers!
The scope and content, e.g.
- All costs of execution
- Cost of "finishing": Training, transfer, startup, etc
- Indirect costs: In-house expenses, overheads, insurance
- Any assets consumed: space, permanently assigned equipment, etc
- Project financing costs
- Allowance for inflation, if the project lasts several years
- Contingencies, scope change allowances, special execution problems, etc