I have no doubt the numbers are soft, that is why i used a multiplier of 10. Even at 150 B, it would be a bargain compared to rocket technology. SE 2010 had quite modest results this year, but it was a beginning. As an analogy, the sponsored contest for having automated vehicles traverse a (100?mi) desert route, was quite modest last year as the furthest a vehicle even went was a few miles. This year 4 finished the course the required time. There is extremely rapid development in automated vehicles and robots interactin with their environment. This will be a period of rapid development for such robots, and I don't think you have realized this. All the enabling technologies are there, and when that happens the development is in fast improvement cycles. There are gillions of analogies--light weight motors leading to scads of hand held automated tools and appliances. IC's by which you use the latest computers and software to design the next generation ( I was in this business for years) is another example.

Bad projections of technology often come before the enabling science has been done (see fusion power), but once the basic groundwork is present rapid development and projections become much more possible. The show stopper right now is the required cable and I grant that until that technology gets close the SE is a dream. But when/if the required cable is able to be produced at reasonable cost, the SE will become an engineering problem that will almost certainly happen. The pace of carbon nanotube technology seems to be going well enough to believe there is a very good chance of its continued improvement to the point of a SE cable. We will see. I would rather spend a few billion making sure that such cable development is fully funded for a few years, along with a 100 other things you could aford for 100 Billion than a single manned mission to mars.