In 2006, ACP estimated the cost of the third set of locks project at US$5.25 billion. This figure includes design, administrative, construction, testing, environmental mitigation, and commissioning costs, as well as contingenciesto cover risks and unforeseen events, such as accidents, design changes, price increases, and possible delays. The cost of interest paid on loans during construction is not included. The largest cost is that associated with constructing the two new lock complexes—one each on the Atlantic and Pacific sides—with estimated costs of US$1.11 billion and USD $1.03 billion each, plus a USD $590 million provision for possible contingencies during their construction.
Opponents contend the project is based on uncertain projections about maritime trade and the world economy. Roberto N. Méndez, an economist at the University of Panama, alleges that the economic and financial projections are based on manipulated data. Independent engineers, most notably Humberto Reynolds and Tomás Drohan Ruiz, the former head of engineering and dredging of the Panama Canal, say that the project will cost much more than currently budgeted and that it is too risky for Panama. M. A. Bernal, a professor at the University of Panama, argues that confidence in the ACP's budget is undermined because of the involvement of engineering and consultancy firm Parsons Brinckerhoff. Parsons Brinckerhoff is best known for the Big Dig in Boston, which ended up costing three times the estimated amount, with several structural and safety concerns.