It may come as a shock to you, but accurately predicting the many costs of a construction project is incredibly difficult. The myriad of moving parts involved in getting a building to stand up and not fall down is so variable per project that many of them see budgets being misappropriated.
The construction industry is a financial whale, too. Since 2016, the growth in the industry has been set to increase 6% to be valued at a whopping $712 billion. Budget maintenance is an essential part of proper project management when that much money is being thrown around by a single industry. Beyond construction equipment and the like, there are costs that aren't the run of the mill invoice items construction projects are associated with.
It's strange to think in an industry that requires the cooperation of several entities striving for similar goals that ineffective communication is the biggest money pit in construction. Between architects, designers, owners, and the several branches of workers on a project, this turns into a multi-headed communication Hydra that eats time and money. Many projects are planned by upper managerial echelons without the consultation of the people working on-site day after day. Planning a project and projecting the cost can't be done purely on a spreadsheet once in the beginning, it requires maintenance on a rolling basis between all parties.
There are a ton of factors that aren't within our control. Global markets, weather, location, acquisition of materials, etc. can change at the drop of a hat. However, the control we do have is how parties respond to these variables and implement action plans. Project management can't be solely done from off-site and can't be effectively done in a managerial vacuum. Sure, perhaps some things are beyond our control to change, but planning around them is key to saving yourself from an avoidable fiscal headache.
Project maintenance beyond the physical work on a construction site boils down to effective, consistent communication. Technology is changing the industry to the point that more and more construction equipment is using automation to share data between inanimate objects. If we're capable of technological innovation to the point that things can communicate with each other it shouldn't be so difficult for human beings to do the same. From planning to putting a project together brick by brick, communication is the mortar to the process that keeps things solid from foundation to finance.