in our model calculations the energy costs are in the same ballpark like labour. thus energy costs are the main culprit. transporting "the light" from elsewhere to the crop has a ~90% loss (20% - 25% solar efficiency times transport losses of 20% times LED efficiency of 40% - 50%). so you need ten times the area elsewhere to be space efficient on a premium priced area. also viewed from crop product pricing the economics simply don't add up. there are much more profitable things you can do on urban real estate.

(I'm working in the field of agricultural economics)

Others (e.g. https://news.ycombinator.com/item?id=17467755) have highlighted that plants only use a few specific wavelengths. Have you included that in your calculations, i.e. are you comparing (sunlight -> electricity -> LED at optimal wavelength -> photosynthesis at that wavelength) vs. (sunlight -> photosynthesis)?

What is the benefit of vertical farming if you need to occupy 10x more land with solar panels than conventional farming?

Solar panels don't require as much water.