How much should a muffler and calilter converter repair job cost?

Sooner or later, most cars will need to have one or more catalytic converters replaced. The old converter off your car or truck can be recycled for cash. Some of the older converters are worth enough to pay for having a new one installed. But most people are not aware of how valuable they are, so they let the muffler shop or repair shop keep the old converter. The muffler shop will recycle the old converters for money that should have gone in your pocket. Personally, I think there should be a law that requires the muffler shops to give the old converters to the customer, or have the customer sign a waiver saying they do not wish to keep the old converter. The waiver should state that the converter can be recycled for cash. And if they waive their right to keep the old converter, the muffler shop should be required to reduce the cost of the new replacement converter by a percentage of the value of the old converter.