I was doing an oil change a couple weeks ago and discovered a crack in the RH exhaust collector of my C180. Upon examination, this part had a lot of field-repaired cracks, so I decided to send it off to an exhaust specialist to get done up right. I ended up sending it off, along with the risers, to Custom Aircraft Parts in El Cajon CA (800-561-1901), who did a bang-up job rebuilding an Avcon muffler from my old C150/150 a few years ago. Got it back yesterday, they did a great job and turnaround was mere 4 business days. They charged me $375 for the collector and another $375 for the three risers, for a total of $750 (plus return shipping) which I consider very reasonable.
before:

after:

Be thankful you don't have Maule exhaust. There junk.

My stuff was actually wasn't that bad..... considering it's 62 years old.
The collector on the other side looks like it's been rebuilt in the past, still in good shape.

Looks great!

Looks even better on the airplane.

Looks good!