$8.3 billion?  I think it will be at the $10-$12 billion mark when it's done, say 10 years from now.  This would be in line with other public infrastructure project.

To get public buy-in, politicians always low-ball the cost and timeline in the lobbying stage.  They know full well that they just have to reach the point of no return, like in this case.  So even more money has to be thrown into the black hole.

Btw, the whole project was designed to enrich the political elite and their friends.  Check where Mufi and his friends are and how they are, financially.