It should be around 59-89 dollars for first half hour.
Typically I have seen professional licensed plumbers charge between $75 - $120 per hour.
Most likely it will start at $300 for first hour and then any additional hours will be between $75-$150.
It varies depending on your location. You should call and check with a few plumbers in your area about how much their service call is. Make sure to ask a few more questions related to your plumbing issue (what’s included / not included with this service call…).
$300 first hr ? I want to be a plumber in your area . most around here are $85 first hr but sometimes in the winter months if snowing or really bitter or after 12am ( emergency call ) will be $ 95-110