I have worked as a research administrator in the Boston area for 8 years, and thus have seen all postdoc salaries in the areas I work (natural sciences, engineering, and computer science). This is not how salary works for postdocs.
- It is set by location. Boston pays higher than other areas due to cost of living. They have to set a rate that is sustainable to meet future commitments as well.
- It is set by funding source. NIH has minimums that must be adhered to. If you don't receive NIH funding, you can pay less unless your institution says no.
- It is set by field. I work in a top research university, known for having high salaries in research positions, including graduate students. Within the same building, there is a $30k disparity in pay between postdocs. Econ CS folks pay $80k because the faculty have to compete with both finance and Silicon Valley stealing their postdocs. Bio-engineering postdocs get the NIH minimum. It's not personal--it has to do with the fields they are in and the competition for postdocs.
Of the hundreds of postdoc salaries I have personally managed, I have only seen PIs supplement if the fellowship pays below the department standard or NIH minimum. If that's not the case here, I would not approach the PI.
The point of you getting an F32 is three-fold:
- You learn how to write a grant on your own.
- You can spend time on your own project, promoting independence in research.
- You relieve the stress of procuring funding for the PI.
[Clarification on the compliance involved with this funding source: F32s are highly regulated; the grants policy statement defines supplementation and additional compensation differently, and it's important to make sure we are explicit about which words we are using.
A supplement, is additional stipend funding that provides no benefit to the PI. Because additional stipend funding must be consistent across the institution, frequently the policy is to use a department standard or NIH minimum as the policy to which a trainee is supplemented. This is paid out as a stipend and is not certifiable effort.
Additional compensation, is essentially a part-time job which allows the postdoc to work on other projects up to a total of 10 hrs/week. This is paid out as salary, and if on a federal grant is certifiable effort.
Unless they provide a part-time job for you (see policy statement), this leads to the conundrum of the PI spending more money on a postdoc who will not work on their grant. Furthermore, you can't work on a grant that overlaps with your own. This is probably why this method is less common than expected; if you request the raise of $15k, these additional funds (stipend, not salary) by definition must be of no benefit to the PI, because F32 Postdocs fall under the "trainee" definition of the Department of Labor. If your salary is $58,500 and you received $15k in salary instead of stipend at the same hourly rate; NIH could cite your institution for non-compliance, because it's technically above the 25% figure that they allow for additional compensation. The funding source is irrelevant. Your institution should have guidance on how they handle F32s. Here's one for UCSF.]
You are currently considered a bonus to the PI and a great relief. Startups don't last forever. They are great for bridging funding when data and results are difficult to procure; funding new research that sponsors won't fund; paying for expenses that cannot be allocated to a grant (e.g., general lab supplies or travel). She's not rich--there is plenty in her future to spend this money on, some of which could be on you (e.g., professional dues or travel).
Research funding is a rough game, so be supportive of her too. There is some risk for her as well, as her future funding is not guaranteed. Funding cliffs can be seriously painful for a PI, as they don't have personnel to procure data, do initial analysis, etc. Everything comes to a crawl, and it's hard to get published or funded when you can't pay students or postdocs. Should this happen, she may become a ward of the department, which will cause her reputation to take a hit with her peers.
If you are still going to approach her, definitely consider how tough her situation is, even if she wants to give you everything you ask for. In the end, you are both at the mercy of limited funds, and her responsibility is to make sure she has the funds to support everyone in her lab that she is committed to.