Why is there something rather than nothing?

It's always seemed to me that this philosophical chesnut isn't a wff. For to ask 'Why is there something rather than nothing?' presupposes that there is, actually, something rather than nothing. In fact, if we're going to pose a question with two terms ('something', 'nothing') then we have to ready ourselves for the inevitable two-by-two matrix:

Why is there something rather than nothing?
Why is there nothing rather than something?
Why is there both something and nothing?
Why is there neither something nor nothing?

Now in two of these cases (the first and third) the somethingness of something clearly trumps the nothingness of nothing; or to put it another way: what would the cosmos look like if there were something rather than nothing? [answer: pretty much as it does now.] And what would the cosmos look like if there were both something and nothing? [answer: pretty much as it does now]. And four reveals two in its true light; not as the exclusion of something, but as the dialectical balance of nothingness (ground) and somethingness (relief), which leads back to the same question-and-answer. what would the cosmos look like if there were nothing rather than something? [answer: pretty much as it does now]

The only question that does not lead us to the cosmos pretty much as it is now is four. And this is a problem. But it is a differently weighted problem than the one implied in the usual formulation of the question: not a 50-50 mystery 'something? nothing?' (which balances ontologically on the knife-edge) but a 75-25 split, weighted heavily on the former term, 'something'. Which in turn suggests one possible answer to the question.

Q: Why is there something rather than nothing?
A: Well, it's not a necessary state of affairs, but it is the more probable one (three times as probable as the alternative). Therefore, as water runs downhill, the cosmos just happened to slide into the probability declivity and here we are.

But how satisfying an answer is that?