These are hydroponic systems, so it'll be distilled water, power for high-intensity grow lights (where stuff grown outdoors, at least in-season, gets this from

These are hydroponic systems, so it'll be distilled water, power for high-intensity grow lights (where stuff grown outdoors, at least in-season, gets this from the sun), nutrient solution (in an outdoor context, some of this would be "free"-ish, from soil, and some would be from fertilizer), plus lifetime-amortized costs of the grow setup: pumps, filters, etc. And all of that besides the water you'd have to ship anyway from wherever it's manufactured. Granted, if we're talking lettuce, it's like 95% water by weight anyway, and a decent percentage of what's left is carbon that's fixed from the air, so there's probably a shipping savings, but I still don't think this whole setup would be particularly cheap.