How much does your average Hydro-electric system cost to build...

How much does your average Hydro-electric system cost to build these days that will produce 88mw

Whatever it is, it's a lot more for pumped storage. Pumped storage is only effective when the primary power is coming from thermal generators running at their design output. A concept study has been done to convert the Snowy to pump storage but that is a multi-billion project. You don't spend those bickies just to use up excess generation on those days when the wind is blowing and the sun is shining.

Point taken on the milli watts, but they were what I worked with in my trade fifty years ago.