"Obviously not enough" is my usual reply with a grin and wink. If they push I'll give them something like "Salary is one of many factors I consider. Once I know

"Obviously not enough" is my usual reply with a grin and wink. If they push I'll give them something like "Salary is one of many factors I consider. Once I know more about the position I will be able to provide a number." Moves the discussion from salary history to salary expectations with the underlying message that they need to impress me not vice versa.