A quick calculation: the total floor area of the Empire State Building is 63 acres. You can do your own calculations for the cost of building the Empire State Building vs the cost of buying 63 acres of land (which, incidentally, gets light) in upstate New York, but I'm pretty sure that one is much, much, much larger than the other.
Frankly hydrogen vehicles are more feasible than this, but only barely.
So what if it didn't replace one major farm and just a small local one? And what if the vertical farm and office building idea were combined, so that you had alternating floors of greenhouses for plants and office workers that ate them?
I'm surprised I haven't seen the ideas brought together before, it seems more pragmatic than a dedicated building just for the farm and there's a growing movement to eat healthier at work. We order from FarmFresh at my offices, which supplies us with fruit and veggies from a local family-owned farm and we've been loving the results.
Also, a lot of farmers really don't want to live in skyscraper land.
It takes 1-2 acres of farmland to support one person's eating requirements, which is two floors of the Empire State Building. Alternatively, there's 21000 people working in the ESB so that's about 200 people per floor. If you devoted every second floor to agriculture (and magically solved the lighting problem) then each worker could acquire 0.25% of his daily caloric requirements from the floor below... maybe a couple of strawberries?
Oh, and the ESB rents for $38 a square foot, so working out the effective cost of each strawberry is left as an exercise for the reader.
I also looked up the average cost of agricultural land per acre in the US, which comes down to about $1200 per acre, or about 0.3 cents per square foot.
This means that for the cost of buying outright the average agricultural square foot somewhere in the country, you could rent that same square foot in a big-city skyscraper for about 45 minutes.
(two floors) x 200 people = 400 floors
(two floors) x 300,000,000 people = 600,000,000 million
Hmm, the world must be really big, or the floors must be really small. If we double that number to include Europe, indeed, lets increase it slightly as Europe has a bigger population, that is 1.5 billion floors of the Empire State buildings to feed only about 1/6th of the world. That does not sound right to be honest.