I currently helping to supervise a bunch of engineering students who are making a design for a one way Mars mission based on the Mars One plan. For three sets of 4 astronauts; assuming SpaceX delivers on their promise of a Falcon 9 Heavy launch only being $125 million, assuming 2023 technology, and only considering the transport of the astronauts (so not sending all the additional base stuff), at a quite early design stage, the cost estimate is $16 billion. Most likely that will increase, and of course the base modules are not factored in. I'm rather sceptical that Mars One can deliver what they promise for only $6 billion. Though for context I should point out that $6 billion is only half of what was spent on tobacco advertising in the US alone in the year 2006 [http://www.cdc.gov/tobacco/data_statistics/fact_sheets/tobacco_industry/marketing/] (Yes that is $12.4 billion, just spent on advertising tobacco!) Mars One is also rather contradictory about the technical readiness, on the one hand they claim they're using off-the-shelf tech that can be delivered today, on the other hand once they gather sufficient funding they will start on conceptual design? Those two statements are mutually contradictory. I don't believe Mars One will succeed (though fortunately they will probably fail long before it costs lives), but I'd be happy to be proved wrong . I'm fine with the concept of sending people to Mars one way, but I don't think Mars One's funding model is reliable enough and a lot of technology still needs to be developed. Yes, there are a lot of concepts of how a Mars base could work, but going from a concept to a working object is always a lot harder than people think. The challenges are definitely not insurmountable, but it's important to realise at the moment we just have an idea of how we might solve the problems, we haven't actually solved them yet.
