[Answered ]-Is it possible to add response examples to non-200 responses

The OpenApiExample object contains a status_code property that is by default set to ['200', '201'].

Try something like this:

@extend_schema_serializer(
    component_name="CostResponse",
    examples=[
        OpenApiExample(
            status_codes=['200', '400', '406'],
            name="A Great Example!",
            value={"field": "Example Value"}
        )
    ]
)
class CostResponseSerializer(Serializer):
    field = CharField(help_text="Thing")

That way you can specify examples per status codes.