Let me go on record as stating that the cost estimate for the Death Star has been grossly inflated by the Administration, probably for political reasons.

A back of the envelope calculation is all we can do for now, and there are few precedents for estimating a project like this, which will take global commitment.

The major cost will be in launching the sub-units into orbit, from the Earth’s surface. Say $50 million per launch, taking a thousand launches a day (probably need roughly 100 launch platforms scattered around the globe) … scales to $50 billion a day, assuming no reduction due to mass manufacture.

The bulk of the light elements can be had from our moon, which reduces launch costs from Earth but means establishing a moon colony for mining and refining. Let’s say that the costs can be split 50/50 between Earth based launches and Moon based launches, and let’s say the Moon based production costs eat up the savings in smaller gravity well costs.

So if there are 2000 payloads/day, that’s $100 billion per day, or enough to employ everybody on Earth.

If it were to take 100 years to complete the project, that’s 37,000 days or so…

Makes the total production costs (not including inflation) at around $3700 trillion. That’s equivalent to the totality of the World’s GDP for roughly 50 years.

Far, far less than the “estimate” produced by the White House.