Unsurprisingly I agree with your first sentence. But, I do disagree on your second: I, and others, can see the costs, and I am not referring solely to the financial costs:
It absolutely means risk of war in the Balkans, Greece/Turkey, N Africa.
Elimination of most of the tourist income on the Med coasts
Endangerment of the biodiversity and ecological balance of the sea
Cause for droughts/flooding seen with other dams https://en.wikipedia.org/wiki/Aswan_Dam
Massive population dislocation in the region of tens of millions
I can go on but the point is what would the benefit need to be to consider this project as net positive?