You can already buy prepared food, the same way you can already get a taxi. The difference is that a self driving taxi will be far cheaper than a taxi, partly

You can already buy prepared food, the same way you can already get a taxi. The difference is that a self driving taxi will be far cheaper than a taxi, partly because it can be shared. A robot that prepared food already exists, it's called a factory, but food is far more variable in terms of people's desires.