Well here is a thought. Are you growing all of this indoors, in a screen house or some kind of shade house?
If you are not growing all of this in total darkness, there will be some "free" sunlight so, your LED costs should not be that high. Actually with sun filtering shade cloths and netting to keep bugs out, LED lights are not necessary at all. Costs would be for cost of running the pumps (unless you are doing Kratky which will only need an aerator and they have even less wattage than a pump and they are water efficient. You will have to take into account the cost of the solution and cleaning of the system after each cycle, plus cost of oasis plugs, cost of seeds and seedling growing costs.
If you set up your beds right, you can use reflective material like white backgrounds and foil to reflect light. All of the light is not going to fall only on the crop. There will be spillage. If you do your calculation, don't do the calculation based on sq. ft of of production but how much watts you need to get light to the area to get the 1500-2000 lumens per sq ft. including natural light and reflectors. Lighting will be a fixed cost not a variable cost. You need to figure out not the cost of lighting a plant, but of lighting the area. Using reflective materials can reduce the cost of lighting. Again, if you are not doing this totally in the dark, there should be ambient light as well that will reduce your lighting costs. Plants in full sunlight receive about 3000-4000 lumens.
I have used a light meter for my yard. Under 50% shade cloth I was still getting up to 5000 lumens and 8000 lumens without shadecloth. ( I did it a long time ago so I forgot the season and time of day I did the test.) Under 70% shade cloth, I got 3000 lumens. Caveat: My shade cloth is only 2 ft above my orchids so it allows more light in than a 50% shade cloth at 5+ feet would let in.
It was hard to follow your calculations, but besides being fallacious to expect the light to be the only source and to only light a fixed area, it looks like your cost was based on kwh. that is a 1000 watts per hour = 1kwh. If you multiply by 16 hours = 16 kwh a day per fixture. Your electricity cost is 8rps/kwh = 16*8 = 128 rps/day (assuming 16 hour days) per fixture. How many 1000 LED fixtures do you have?
128 rps/day x no of days till harvest (30 days) = 3840 rps per LED fixture for a 30 day growing cycle. Multilpy that number by the number of fixtures and you will get your monthly cost.
I also could not understand your yield logic. If you are planting 16 plants per square foot, which would be impossible to get good yields, unless you have plants of different sizes. they would all be small. A full lettuce head needs 6-8 inches to yield a good sized head.
I'll do a calculation I know. lettuce spaced 8 inches apart in a bed 4x100 ft = approx 1200 heads in 30-45 days depending on the growing season. 1200 head after taking off the outer leaves and cleaning yields about 150 lbs of salable product. A 1000 watt LED fixture can illuminate approx a 4x5 ft growing area or about 20 sf. If this lettuce bed I described only has LED light as its only light source then it would take: 100/ 20 or 5 (1000 watt LED fixtures to light this area) If you are growing 100 sf of lettuce in this bed at your 8rp/kwh cost then for 30 days your cost would be 3840 x 5 = 19200 rps per month to produce 150 lbs of lettuce. 19200/150 = 128 rps per pound = cost of electricity to produce a pound of lettuce exclusively under grow lights. You are estimating roughly a pound = 500 gms wt per head of lettuce. I don't think with your spacing you will get that. Occasionally we did get a 1 pound lettuce, but most of them only weigh in about 170 gms or about 6 oz with 8 inch spacing. The lettuce we grew was manoa so it is a mini loose leaf variety so it does not weigh much and it sells now for about $4 lb. this is with 8 inch spacing.
You may be over estimating your cost of LED light. Even if it is a 1000 watt LED light. Is it the actual power draw of the LED light or the equivalent watts of a standard bulb? You need to calculate your electricity cost based on the actual watts used by the LED and not its equivalent wattage to a standard bulb. The LED fixture may only use 75% of the watts used by a standard bulb so you may be overestimating the cost. Your actual cost may be 25% lower (on average). It still is expensive if you also factor in that the LED costs way more than fluorescent bulbs. If you can do the hydroponics in an outdoor setting or can get some natural light in, then you should not need to spend so much on lighting.
https://hydrobuilder.com/learn/grow-roo ... Calculator
Consider growing micro greens. It is a faster harvest with even less inputs per sq ft. It has a higher price point if it is popular in your area. Do a market analysis to see if there is demand for it.
Happy gardening in Hawaii. Gardens are where people grow.