$600/hr is the equivalent of about $1.2M/year salary. That's exceptionally rare. Unless you're being cheeky with "should be", I think you have beliefs that are misaligned with reality.
Hourly billing rate has to cover all the hours you can't bill for, PTO, health care, everything..
Most contractors I know don’t work 40hrs day, every week. Also if you look around at advice you’ll find that you shouldn’t quote an hourly rate, you should quote “for the job”. If you’re good and the work you’re doing is even mildly specialized you can get a job done quickly enough that the effective hourly rate is pretty absurd.