Interesting. I think there’s definitely a “meta-game” that negotiation requires you to prepare in advance if you want success. For example, knowing if the job opening is in a “cost center” or “revenue center” for the company, or how the job is funded. Clearly a well-funded department can offer more salary, and a revenue increasing job can pay more than a cost-savings one, since revenue has no upper bound and savings is bounded. Companies that have high revenue per developer can pay more in general. Companies that have to compete globally for talent have pay more than those that only have to compete in a local market. I can go on but you get the idea.

As a hiring manager and someone who’s an employee rep on the 401k committee, I can’t even imagine how I could customize the 401k for an individual candidate. I think the same is true for health insurance.

If someone came with that request, I’d probably be amused but I doubt I could change anything.

We're you willing to walk away if you didn't get what you wanted? Or were you just hoping they would capitulate? IMHO, The key to negotiating is knowing where your red line is, and being willing to walk away if you don't reach it.

Sure, because you personally aren’t in a place you can just leave it.

If you don’t have a good competing alternative offer/option, you’re not negotiating, you’re begging.

And chances are, they have alternatives.

Something is going on here. If the company and team is excited about hiring you, there will typically be some flexibility unless you are already coming in at the top of their range, or above. In which case they should be telling you so, and even somewhat apologetic about it.

If that's not the case, they are not excited about you (in which case, why are they hiring you?), or you have not made your case firmly and clearly.