It's like this, as far as I understood things they were supposed to still be trying to gather the financing to make this viable. The only part I've been suspicious about was them claiming to have the project up and going within 3 years. Of course then again I've also suspected the whole idea was to start building things, fire up public excitement, and then hopefully secure the rest of the funding later. Most of what makes this seem shadowy is that right now they haven't done a whole lot, but then again to my knowledge they have yet to actually put together the six billion they mention as needing.
As far as the actual cost of a mars expedition goes, the only reason why governments have not done it is that as a general rule politicians are too weak willed and would rather spend money for short term political gains by fighting the symptoms of problems coming from resource depletion, overpopulation, and other issues rather than pursueing long term solutions like space travel which while they could take generations to see returns would be able to obtain minerals and eventually living space. This is one of the reasons why I've mentioned that earth could really use a forward thinking tyrant or two rather than a bunch of sheeple elected politicians only thinking as far as their personal benefit at the moment. Of course this is a philosophical argument that goes well beyond the topic at hand here, and it's a matter of weighing the pros and cons. The bottom line is that in absolute terms I have no doubt we could start colonizing Mars, putting bases on the moon, etc... if we decided to dedicated the focus to it.
The biggest tangible problem I've always had with Mars One has been the lack of legal problems, which is also my issue with a lot of private space research companies that make great claims. For example just wanting to store vast quantities of rocket fuel to test boosters and such is going to be a big deal, and of course any such facility is likely to face tons of NIMBY sentiment when people want to build the gigantic storage tanks and such for it.
Of course the other part of this that makes me think scam is of course a little different as well, namely that few of the people selected seem even remotely qualified to make this trip. The idea here being largely to establish a functional base, even if the people are going to die off. This means you'd expect them to have redundant engineers and a lot less people in the field of say physics, who might be qualified to do research, but don't exactly have any practical survival based skills. Not to mention the ages and such involved.
That said Mars One itself has yet to respond so we'll see if that happens and if so what they have to say. It's not just that I'd like to believe that it's real, but also that it seems that the people claiming it's a scam are largely being paranoid, perhaps not without justification, but right now there is no evidence one way or another.