What’s the exploitation? A company offers a job; if the job is appealing to the candidate, they freely take it.

That’s true whether it’s a $250K/yr offer or a $36K/yr offer. In the vast majority of cases, the alternative to a company offering $36K/yr is not for them to offer $250K/yr but rather to not offer a job at all.

If anything, I’d argue that a company offering a consistent salary for the job anywhere in the world is acting more ethically than one offering $X in Mumbai and 5*$X in Paris.

When one asks a question in the format, “Are you pretending that [obvious problem] isn’t an ethical problem?”, it makes me wonder if that person is really interested in understanding or is just interested in accusing someone else and picking a fight.

If it’s the former, then maybe consider that other people don’t see the issue as the same [obvious problem] as you do, instead of assuming that they do, and then basing further reasoning on that bad faith assumption.

If it’s the latter, then continue doing what you’re doing.

You sound dishonest. Surely, you are aware that keeping salaries secret and having them differ between employees assigned to the same job is increasing information asymmetry?

It has apparently become fashionable to voice a concern in response to a solution to that concern to criticize the solution. You're effectively complaining that transparent pricing will result in information asymmetry or exploitation.