Two SUs illustrate DPC ;)
Case Study: The Sui Gas Department - (whether govt. or private, I don't know) - always ends-up below budget. They always save around, say 20 crores given 80 crores as budgeted amount. Glorious! Well, may be not.
Solution: The reason why they always end-up below budget is because they always estimate well beyond what can possibly be required; and on the top of that, when they do stuff (nasty stuff), they follow the golden principle of deliberate planning chaos. Example, "Is this repair & maintenance you're doing already planned in the budget?," asks a sane manager. "Budget mein tou nahi hota, magar yehaan tou aisay hee hota." ("It wasn't budgeted, it works that way [of jahalat, ignorance].") Nothing is planned, sab chalta hai (all non-sense works, they say).
(Appendix: You might be shocked to know that Pakistanis have consumed, thanks to MNAs etc., 60% of Sui gas reservoir, and above all, there's a misconception that Sui Gas field is something huge. Our professor completely denies that, b'cause it's not huge compared to the demand of it.)