Can guarantee it's not a zero sum haggle.
A comp package has a salary number, it also has bonuses, commissions, stocks, options, IP ownership, holidays, work from home time, days/week, travel requirements, travel policy, mat/pat leave, non-competes, and myriad other options that effect the salary number you arrive at.
If you agree to a salary number without taking these into account, they will necessarily disadvantage you on these.
When someone asks, what is your salary expectation, you answer, we're using the same market data and it's really a question of the total package.
A lot of people are only interested in deals that screw you. This is a super fast filter to find them.