Hi Henrique, thank you for replying!

I agree this is not always easy, but there are many ways to solve it.

In the Israeli community there's an annual survey which provides good data around design salaries. So it may not be 100% accurate, but gives a good starting point. For any other case, I would just suggest asking an experienced designer, what is a fair salary for a designer with X experience. Also tools like LinkedIn, Glassdoor and Indeed can be leveraged for the task.