EuroATC,
Of course it isn't the health insurance premium that makes the difference.
But tax does, and in this case (comparing GVA with ZRH) big time.
And don't get me wrong, I'm not trying to encourage people to apply, without fulfilling the basic requirements.
However, it is not the case that french (in GVA) or german (in ZRH) would have to be your first language (as you suggest) in order to be able to validate.
Just think of all the swiss germans working in GVA...