You do know that the cost of any Project depend's on
Accessibility,
Required Infrastructure development,
Working space,
Availability of Raw materials,
Purpose of Dam,
Long term Plans,
and
Type of tender/project. right ?
Do you know that Diamer-basha dam will cost 14+ Billion US dollars for Production capacity of 4500 MW. it's like US 1 billion dollar for 321 Mw. making 578 MW for the same cost of 1.8 Billion US dollars at which Sahiwal coal Project will produce 1320 MW. So why even make Diamer-basha dam then ?
Normal People do not "see'' things on basis of "cost and production" only. Hydro-power projects provide much more. THEY STORE WATER. and they provide you electricity for Rs.3-4 per unit. unlike Coal which stand at Rs.9-10 per unit.
Similarly for Coal power projects, Furnace oil projects and natural gas projects you need SUPPLY. supply of fuel. which cost fuel+transportation charges. You are free from this headache in case of Hydro-power plant.
next come Environmental aspect. which i think you already know about.
Are we good ?