I see this as the core of the argument - paying people based on their needs requires you to invade their privacy in order to find out their needs. And not wanting your employer to invade your privacy would mean getting some baseline low pay because "you don't have any needs".
If I go to the grocery store, I do not pay more for an apple from a farm owned by a family that has a sick grandma than from a farm owned by a family that does not have a sick grandma.
In my role I know that and would also support that case as special.
This kind of thinking varies depending of where you live (at lease for most people and less for remote workers). My takeaway is: if you live in a country/state where this help is "embedded" within the system we can focus more in salary equivalence for the same job responsabilities but if you live in a place that put this pressure on the organization side the organization could have the awareness to take care of these issues. In HN we have people from all around the world and with different democratic and non-democratic systems.
How would you? Are you running an intelligence agency and it's part of your job as a boss to constantly monitor your employees?
I don't see how the location matters, really. A single person might need more money because they want to save up to start a family. Now you factor that in, and you pay them more, but they never find the right partner and don't start a family. Are you now going to ask them to return the money?
I'm a terrible example, but if you offered me to work the same (or, let's face it, often more) than someone for less money because they're married with children, I'd rather work somewhere where I'm not a second class citizen.
No, I live in a culture where this matters arise. There are many discussions in this thread based on culture experience. I see for example privacy discussions, in some cultures/countries privacy is a must but at the same time contradictory with the private information that is flowing unregulated in multiple organizations.
It seems like it's not the needs that matter, it's your assumptions about them.