JO does have a legit point...

Unions, not management, primarily determine how the pilot compensation pie is split up.

At mainline senior pilots fly bigger airplanes, which generate more revenue so it's reasonable they get paid more.

At regionals that model barely applies, so the income split has more to do with who's been around long enough to have control over the system. If senior pilots had their way new hires would get paid nothing at all, but the left lateral limit on that is that the company knows they have to pay at least barely enough to actually attract new hires. I've seen the company negotiate increased new-hire rates but I have never seen a pilot group make a big issue out of that. The pilots seem to feel that new-hires are the company's problem.