Money doesn't actually exist, you do understand that right?
There is little reason to go on about "cost" or "money". At this point in the history of the world, money doesn't exist. What exists is "opportunity" that is printed in the form of what used to be called money. World banks and governments control the expansion on the planet by using "interest rates" as a deterrent to rate of growth. The lower interest rates are at the Fed and other "world banks", the more opportunity there is to do something, because you don't have to pay it back with any great "loss". The world truly is now a socialist economy that is being ran by the bank's dictatorial policies. They try to do the right things, it seems, by managing the rate of growth based on the stock market, population and perceived "inflationary pressures".
But, in the end, all that is really happening, at this point, is the lack of "projects" is limiting the employment on the project, and that is directly related to the "interest rates" at the bank, and our in abilities to have long term views on projects, such as this one, which it wouldn't really matter if we were able to complete. Instead, it would employee 10's of thousands of people with a job to complete, money to be made, and things to keep lots of parts of the world employed doing.
It's time for us to really start understanding that the way we view capitalism and opportunity really has lots of issues with how successful we can be at keeping the world running.
We need large scale projects that aren't "WAR", which is what has been the single largest employer we've had. We need to try space exploration from a different perspective than "jump to orbit and look at the earth". NASA's small vehicle projects, going out to look at lots of different things will be very educational, and hopefully reveal some rather amazing things, right here, close by.
But, with gravity as our barrier, we can't get much "mass" off the planet to go do anything "long term". Instead we have all these 1-2 week outings to orbit, and that's all we do, over and over and over...
How long do you think our societies can survive on "build cars", "build houses", "grow food", "birth another baby", "bury another relative", buy another stereo, get the latest iphone etc?
There is much more in the universe that we could be discovering... We waste an awful lot of time, energy and ohh, that "money" stuff on completely useless things.