We’ve been talking about your employer as an abstraction, but in the instant case you’re talking to an actual person.
Let’s call him Bob. It is Bob’s job to get you signed with the company as cheaply as possible, but Bob is not super motivated to do so, because Bob is not spending Bob’s money to hire you. Bob is spending Bob’s budget. Bob generally does not get large performance incentives for shaving money off of his hiring budget: you get a new Macbook if you convince Bob to give you $5k extra, but Bob gets (if he is anomalously lucky) a dinner at TGIFridays if he convinces you to take $5k less. In fact, there are many organizations (and Bobs) for whom power, status, and money come from asking for more budget every year. If you turn out to be on the expensive side, that is great for Bob, because
a) he manages a high-powered peon so he must be a high-powered manager
and b) this will help Bob get more budget next quarter.
So if you’re worried about what Bob will think of your moral character, or you want to compensate Bob because you feel you owe him for this job opportunity, do Bob a solid and negotiate in a spirited fashion with him.
You don’t owe Bob for giving you this job opportunity, by the way.
Internalize this: everyone in this discussion is a businessman. (Some might call themselves “regular employees,” which just means they’re businessmen with self-confidence issues and poor business skills.)
What a wonderful article! Salary Negotiation: Make More Money, Be More Valued
The second implication is that the inner serf worrying “If I even attempt to negotiate this, the deal will fall through” is worrying for nothing. They’ve got thousands invested in this discussion by this point. They want you. The absolute worst outcome of negotiating an offer in good faith is that you will get exactly the contents of that offer.
Let me say that again for emphasis: negotiating never makes (worthwhile) offers worse.
This means you need what political scientists call a commitment strategy: you always, as a matter of policy, negotiate all offers.
(In this wide world I’m sure you can find a company who still makes exploding offers, where you get one yay-or-nay and then the offer is gone. You have a simple recourse to them: refuse them and deal with people who are willing to be professionals. You’re not a peasant. Don’t act like one.)