> The only way vertical farming becomes reasonable is with cheap energy, and high food costs

I'd argue it'd only become tenable with high land costs. The cheaper energy is, the less sense vertical farming becomes since it makes the transport costs from far away, cheap-land areas even lower. If real-estate in and out of a city are roughly the same (no cheap pasture land!), then the farm can be more or less any location, that includes in a city. But for that to happen, would probably imply some kind of Judge Dredd continent swallowing city first.