As greenyoda already pointed out, there can be people who make 140K who don't mind making a lot less than they did in their last job. My dentist decided to quit and become a musician. A friend took a job with a pay cut because his wife moved for her job - it's easier for a system admin to find a new position than a philosophy professor.
In any case, you don't like employers who eliminate based on a single point of information, so you must not like an employer who eliminates candidates only because their current salary is well over the available funding. That doesn't sound like you like their use of that information.
And that signal level is going to be lousy. The primary signal is the job roles/work experience. I can't see salary adding much useful information. In some areas, like government, salary is closely tied to one's job position, with only some variability based on skill level. There's almost no information there in the first place, much less something that's easy to disentangle.
It would also say that Lilly Ledbetter wasn't as successful at her job as her male counterparts, because she was paid less, even though the reason she was paid less was due to 1) discrimination on the basis of sex, and 2) a policy of not revealing salary information.
If someone wins the startup lottery then spends the next few years working part-time to spend the rest of the time working on Linux kernel development, then said employer will regard the person as being unsuccessful, because options aren't part of the salary information.
At another friend's startup, the employees took a pay cut for a year, to help with cashflow problems while they did a pivot. That didn't work, so they looked for new jobs. Again, your supposed signal would indicate that those employees must each be individually unsuccessful.
Sure, asking a job candidate about marital status, or children, or where the candidate goes to church is not "unethical in and of itself." But these are not standalone questions completely uncoupled from the interview process, so your idea of splitting is apart is somewhat ridiculous.
Again, I say that all salary and income information should be public. Then all sides will have an idea of what the market is like. The salaries for government employees in the US are public, as are all the salaries in some countries, so it's not like keeping this information secret is essential for the organization's well-being.