Catalytic Converter on 2003 SL 500

[travler1029]

What should I expect replacement costs to be for catalytic converter on a 2003 SL 500?

 

[LostKiwi]

Are you sure it needs one? They aren't a common failure point.
There are 4. One per bank in the exhaust manifold and two under the car.
Which do you need?

 

[brandwooddixon]

Assuming that any of them actually needs replacement, you may need to look at aftermarket sports suppliers of approved parts to keep the costs down.
I'd look at other issues that may be causing any emissions failure before replacing the catalyst e.g., high hydrocarbons may be caused by leaking air intake or vacuum system, poor ignition, worn piston rings, leaking valve stem oil seals, inefficient oil scavenging on the breather system just to name a few.