Well, a whole lot more expensive than a cathedral anyway. There's an estimate here that the cost of rebuilding Chatres between 1194 and 1223 after much of it was destroyed in a fire amounted to around fifty million dollars adjusted for inflation. But that's said to be a conservative estimate and it is 1972 dollars.

Chatres Cathedral - cost to rebuild most of the cathedral in the early twelfth centuryabout 50 million dollars in 1972 money. Or around 260 million dollars in 2010 money.

There's another estimate here though, that is in terms of annual yearly wages for the labour.Santiago cathedral used a workforce of 50 skilled labourers from 1075 to 1211. So, that's around 6850 labourer years. The average US wage for a stone mason is around 40,000 dollars, so that works out to around 274 million dollars. Converting back to 2010 dollars, that's around 250 million dollars. That's just the labour, you also have to pay for materials. They estimated an equal cost for the materials. So that's around a half a billion dollars.

So, if that's a good rough estimate, you could build three hundred medieval cathedrals for the cost of the ISS. Even if that estimate was an order of magnitude out, it's clear that the ISS is way more expensive than a medieval cathedral.

There's an estimate here for the Great Pyramid, that it would cost 878 million dollars in today's money - that's building it today with the current cost of the limestone and the labour.

What it would cost to build the world's most famous landmarks today

Kheops-Pyramid Great pyramid of Giza, 878 million dollars if built with today's materials and modern labour, build 170 of those.

Best I can find there. We could rebuild 170 great pyramids for the cost of the ISS. How that compares with the actual cost to the Egyptians I don't know.

This is perhaps the closest in actual cost to the ISS, so it would be interesting if anyone has tried to figure out what it would cost them.

There's an estimate here of the total hours for building Stonehenge - about 675,000 hours. THE COST OF BUILDING THE STONEHENGE COMPLEX

So - taking 34,000 as average annual salary for a labourer in the US, and 2,080 hours a year, that's 34,000*675,000/2080 or about eleven million dollars.

That's the equivalent of 325 people working full time for a year. You might be a little surprised that so few people could build Stonehenge - but they had sleds and other quite sophisticated equipment. In practice this work was spread over many generations.

Stonehenge (credit Diego Delsa) - eleven million dollars worth of labour, could build 13,600 using neolithic methods

So we could build 13,600 Stonehenge monuments, using neolithic methods, for the cost of the ISS.

So, the claim seems reasonable to me, as best we can guess. It's amazing how much a few hundred people, working for a year, can accomplish, so probably many of the other ancient monuments would come in at similar costs to Stonehenge, medieval cathedrals, or the pyramids.

There's another way of looking at it though. Compared with the total economy and the number of humans now on the Earth, it's not such a huge cost.

Back when they built Stonehenge for instance, this may have taken much of the effort of an entire community for generations. So - as a percentage of their economy, it might well have been higher, even if adjusted to US dollars, e.g. counting the cost of the number of workman hours they put in, it might not cost that much.

I think would be hard for anyone to answer that.

COMPARISON WITH GROSS WORLD PRODUCT

But the Gross world product is US $87.25 trillion in purchasing power parity.

Compared with that, it is 0.17% of the yearly gross world product - but spread out over many years.

Equivalent of one person out of every ten thousand throughout the world working on it for the last seventeen years, if I've got this right. It is a pretty major project for the world to undertake, seen that way. But probably not such a major effort as Stonehenge.

I am in two minds about the ISS myself. Depends on whether I wear a "science hat" or a "political hat" :).

SCIENCE VALUE OF THE ISS

I don't think those costs can be justified by the research alone, because we could have built it as a telerobotic facility operated from the ground, and done nearly all the same research for far less cost except the research into human effects of weightlessness. I don't know of any comparison study, but without the need to send humans there every few months, wouldn't be surprised if that would have cost an order of magnitude less.

Also, it gives us experience in humans living in space, but it's not a research priority to find out how best to sustain humans in closed systems for long duration spaceflights either - it would be built differently if its primary purpose was to prepare for interplanetary flights or a return to the Moon.

So it seems a bit of one thing and a bit of another - mainly a zero gravity lab, but operated by humans with some human factors research, but not prioritized for that (or there would be far more focus on such things as developing closed systems, growing food in space, generating oxygen from algae, and artificial gravity research).

And using humans for the non human research is not the most efficient way of doing that research in terms of cost. If your main aim was to build a zero gravity laboratory in space, and if you didn't have the (very natural) political requirement that you have to have astronauts on board 24/7 and give countries involved as many as possible opportunities to send astronauts there - without that requirement - I don't think you would build the ISS.

I think that - probably - you'd build a lab that can be operated from the ground, with humans visiting it from time to time for maintenance and to set up experiments etc.

At any rate, you'd have seriously explored that possibility at least and done careful cost comparisons to see whether and for how long you needed humans in space to keep it all running, and made it so you can run it from the ground as much as possible, because, obviously, man hours in space are expensive.

It costs the equivalent of an astronaut's weight in gold to send them to space for one week, at least going by the amount the Russians charge tourists on the ISS. How much does it cost to ferry an astronaut to the International Space Station?

If you had to justify it as a science project, competing for research grants with other big budget science projects - then you'd have a lot of explaining to do, to show why you want to run it this way rather than telerobotically.

HUMAN VALUE WITH SCIENCE AS EXCELLENT "ADD ON"

But on the other hand it is hard to assess how much value it has had in terms of international co-operation, and the astronauts view on the Earth from space, and other intangible effects. And that wasn't their mandate, to build either a human factors research station, or the least cost way to make a zero gravity lab.

It was sort of like Apollo, politics led and then adding as much good science to it as one can.

And given what it is - it does do a lot of excellent scientific research.

If it has as much as saved us from a single war also, even a minor war, through co-operation in space, then it is well worth it. And the countries involved spend far far more on their military programs than they do on the ISS.

I've expanded this and made it into a post for my Science20 blog here: Is The International Space Station The Most Expensive Single Item Ever Built?