Cost of replacing a circuit breaker will depend on the amperage of the circuit breaker.
If you can replace the circuit breaker yourself it might only cost $10.00 to $50.00 depending on the size and amperage of circuit breaker.
Larger amperage circuit breakers cost more than the lower amperage ones.
If you have an electrician do the job then it will cost you a service call cost which could be $100.00 and then another $100.00 to replace the circuit breaker.
So having an electrician replace the circuit breaker could cost $200.00
If you don't know what you're doing then don't mess with the high voltage circuit breaker panel and pay the money to have a professional replace the circuit breaker since you could get electrocuted working in the panel.