So to review some basic concepts:
NPCs are supposed to accurately predict what sort of need-based financial aid award the college in question will give you, assuming you submit the same information when actually applying for aid.
The CSS Profile is a College Board service which participating colleges can use to help determine their need-based financial aid offers. And one critical thing to understand is the colleges can (and do) decide for themselves how to take that information and turn it into offers.
To help understand that, it is useful to know there is something called the Institutional Methodology (IM), which is a sort of baseline analytic approach the College Board will provide. This is in distinction to the Federal Methodology (FM), which is associated with FAFSA. Here is a primer on the IM if you are interested:
And when people talk about how the CSS treats various issues including income and assets, usually they are de facto talking about the IM. But again, CSS colleges can and do vary from the IM however they see fit. A common example is the treatment of net home equity. My understanding is the IM treats it like any other asset and assesses it at 5%. But some colleges reduce or even eliminate that assessment, others apply it but only up to a certain cap, and so on.
That variable treatment of home equity could be seen as one way in which CSS colleges can de facto adjust for HCOL scenarios. Generally speaking, at least home-owning families in HCOL areas tend to end up with a greater portion of family wealth in the form of net home equity. So if a CSS college eliminates, reduces, or caps the assessment of net home equity, that is de facto going to tend to help out more families in HCOL areas (again, at least the home-owning ones).
But to come full circle, a college’s NPC should reflect all this. So, a CSS college’s NPC should ask about net home equity if it assesses net home equity, and then it should assess the reported net home equity the same way it will assess it when actually determining a financial aid award.
So, to the extent a CSS college is de facto giving a break to HCOL families in this, or any other, way, it should already show up in its NPC as well. That system is not always perfect, but generally speaking I would not assume a more favorable result than the NPC is likely, barring a material change in circumstances.