OK the cost of building a wind Turbine averges ~$1.3-$2.2M/MW... so if we need 450,000 MW it would cost...Yeah, if you are ignoring the fact that they will also be using solar and hydro.
But even your number of 22,500 doesn’t seem to crazy, as you said the USA installs 3000 per year, over 10 years that’s 30,000.
$558 Billion Dollars - $990 Billion Dollars US...
How much do wind turbines cost?
www.windustry.org
For comparison the largest solar park in the world is the Bhadla Solar Park which cost $1.3B US and generates 2,245 MW... So the cost to generate 450000 MW... would be $260 Billion Dollars USD if the plant was built under the same constraints in India... I don't think that Australia costs are the same as India costs...
Bhadla Solar Park - Wikipedia
en.wikipedia.org