There are 2 things to consider here:

1. Passing the same data to `Response` is hardly an option given that one is waiting for a context `dict` when the other is dealing with a serialized content. There is an explicit example for that use-case in the DRF documentation: http://www.django-rest-framework.org/api-guide/renderers#varying-behaviour-by-media-type

2. Using `get_renderer_context()` to add additional info is fine but it doesn't work for values computed within the main method call (see above for the `total` var for instance) or I didn't get how to fill it dynamically.

I agree that the current implementation is confusing, I'll push something more explicit about that.