I am a designer. My best year was about €120K before taxes.
I have no problems getting full-time jobs for longer periods of time. If I'd work 5 days a week and take vacation days as if I'm an employee, I could probably do €180K before taxes but I choose to spend some time on other things.
Now I'm splitting time between clients and my own startup, so one quarter I'm doing 0 and the next I'm doing €30K.