Obviously people might not like it, but can you summarize the moral arguments against it?
For example if a vaccine for an infectious disease was priced higher for people who are more likely to be exposed to that disease (because they have a greater willingness to pay), it could create an unfair burden on this buyer segment and even place the overall population health at risk. Just because a seller knows they have greater leverage over this vulnerable population.
Arguing, even correctly, that price discrimination is bad for healthcare does not necessarily imply that it's bad for other things. Healthcare is different.
Parents a and b are considering whether to enroll their children in a private school.
Parent A lives in a nice neighborhood that can lobby for better funding for public schools.
Parent B lives in a worse school district.
The private school realizes that parent B has worse options, and that they can upcharge parent B. The private school knows that at a certain price point parent A will simply decide to send their child to the high quality public school in their district, so they charge that parent less.
Parent B is disadvantaged because they have weaker bargaining power, and the price discrimination is simply exacerbating existing inequalities in the community.
I don't think that price discrimination is inherently unethical. But the criteria used to discriminate can certainly be unethical. Look up "reverse redlining" for example.