If you can replace the catalytic converter yourself then it will be much cheaper and only cost you the cost of the new catalytic converter.
But you need to be able to weld the catalytic converter on so if you can't do that then it's best to hire an exhaust repair shop to do the job quickly.
Catalytic converts can cost around $1,500.00 to $3,000.00 to replace depending on make and model and year of vehicle.