One could easily come to the conclusion that getting electrical energy from Space is too expensive.

Let's look at total costs.
But first let's look at total cost to tax payers, which are
"necessary" because unnecessary taxes and expenditures
by politicians is immeasurable.

So, I suggest the govt spend 1/2 billion on what I call
"water in orbit".
NASA is spending say 100 to 150 billion on Manned Lunar Program.
And then NASA spends say 200 to 300 billion on Manned Mars program & other sundries.
Total in billions in most money expected spent:
.5
150
300
450.5 Billion dollar

So, I'm only including govt costs related in some way to
this enterprise.

Now, let's look at how much money the private sector would spend BEFORE having a chance of making solar panels in space to sell power to Earthlings on earth surface.
Now, keep in mind that the private sector has no means using the threat of imprisonment in order to get money. And it will get money by people choosing to buy something that they want for some reason. So, in a sense, the private sector gets money by citizen voting by giving money for something. But regardless of why money is spent, it's still money spent. One could say it represents effort and time of humans which they could choose to spend on something else.
So total money spent related in some way with such an enterprise.
Gas station[s] in LEO:
Buying water: 10 billion- 10,000 tons at 1 million per ton.
Total cost to build and operate Gas station: 2-4 billion
Total revenue from gas station: about 30-40 billion [rocket fuel price: 1000 to 3000 per lb- lower price as market matures. Can also get revenue from other sources than rocket fuel [not included]- think of gas stations on Earth]. So number of total cost for a couple decades:
About $50 billion

Gas station[s] in higher orbit than LEO:
Buying water: 60 billion- 30,000 tons at 2 million per ton
Total cost to build and operate Gas station: 2-4 billion
Total revenue from gas station:
About $100 billion.

Gas station on Moon:
Buying water: 100 billion- 100,000 -200,000 tons at 1 to 1/2 million per ton.
Total cost to build and operate Gas station: 4-8 billion
Total revenue from gas station:
About $200 billion.

Now the above is pretty fast for within "couple decades"- a slower pace would be to 1/10th water bought- and therefore about a 1/10th the total cost/price. Whether a fast pace or a slow pace, the amount of water used will be relatively small in first couple to few years- the pace has to do with how much exponential growth there would be. A true gold rush type frenzy could be a faster exponential growth than depicted above and is probably not desirable.

[I should point out that if we continue this pattern of delaying this from occuring, that a gold rush frenzy becomes more likely and less likely preventable. And had NASA/US govt done this kind of thing a decade or two earlier, it might have avoided some wars that have already occurred, and prevented or made less likely some wars which might be in our future. Of course, I imagine many others have the opposite opinion- I suppose based upon the notion that less energy available [less activity in general] makes humans calmer.]

List of potential users of Rocket fuel in space.

NASA- but any of that cost is accounted above- NASA shouldn't buy rocket fuel unless it lowers their cost, and therefore lowers the total cost of say the Mars Manned program or any part of Lunar Manned program.

Lunar water miners: Assume a total of 200 tonnes of payload to lunar surface. Per ton cost from earth surface to space: 5 million per ton- $1 billion. LEO to lunar orbit:
800 million. From lunar orbit to lunar surface: 1.6 billion.
Leaving the Moon: 200 million. Total 2.7 billion.
Entire cost: about 10 billion

Lunar dirt miners: could sell 1000 tonnes lunar material at earth surface at $100 million per tonne:
$100 billion

Lunar tourists: 100 people. Mass: 400 lb per person:
20 tons. rocket fuel cost: .27 billion to surface. .3 billion
to return to Earth.
Entire cost: $5 billion
Other space tourists:
Entire cost: $5 billion
Suborbital tourists:
$200 billion

Constructing bases/houses/labs/hotels.
$10 billion.

Mining & processing metals:
$20 billion

Making solar panels:
$50 billion.

Public works- govt/non-profits/universities: museums, telescopes, safe storage, roads, ports [including mass drives]. Etc.
$100 billion.

Miscs:
$100 billion.

So NASA's price tag is about $450 billion.
And non NASA price tag is $950 billion.

Which totals 1.4 trillion.
And then add the cost of building solar panels to provide
electrical power to earthing. So 1-2 trillion dollars.
So at most about 3.5 trillion dollars.

The 100 sq km solar panel from above, produces
14.54 trillion Kw/h per year.
Humans paid about 10 per Kw/h, so 14.54 trillion Kw/h per year is worth about $1.45 trillion per year.

Considering that Earthling a have already spent about 1/2 trillion dollar playing with the Kyoto agreement, and if they are relatively smart will only end up spending about 1 trillion dollars.

It's a pretty good deal.