Why would they need to sell stuff? Those that own the production facilities can just produce anything they need or want in their own factories. They become self contained in their factory mansions with no need to interact with the 99.999%
What we, the 99.999%, do with our life is up to us. My suggestion would be along the lines of taking over those automated factories, making them state-owned (or taxing the 0.001% with a 99.9% tax rate), and giving everyone a base income.
If everything can be made by robots, there is no need to work any more. Capitalism breaks down. Don't try to apply our current economic models to such a situation. Instead, try to come up with new economic models, and a transition path.