[TamDenholm]

One thing you should mention is that while salary isnt your only incentive, not enough salary is a massive disincentive. You may not be taking the job for the money, of course you're taking it because its an awesome company, with awesome people and you love the problem they're working on, however, no matter how amazing it is, if you dont get paid enough, its not worth it.

Its not their job to tell you how much you can live on, they can make an offer, which should ALWAYS be pushed back upon with a counter offer until you come to an arrangement. Also, golden rule in negotiation, is be prepared to walk away, otherwise, you lose.

As Phamilton says, just say "I'd prefer not to disclose that." and perhaps add, "I will take any offer under serious consideration."