Great summary! I have read all your latest Farming Tales in detail and because of that I took a closer look and made my own calculation sheet like you have :)
I have started playing 1 week ago and invested in some animals and in a Greenhouse.
You are right that at the current seed prices the gardens are not profitable if you have to buy the seeds and it's also better to sell them. But prices are already dropping and I am looking forward to New Waxchester when the harvesting will end up in materials instead of SEST.
I like your hint with the waste of water because that will cost money! I am just missing the count ingame like in the Taco app.
For your own calculation take into consideration that the Greenhouse also needs 1 Water per Day. These would be the missing 4 Water for your Common Water Tower and 4 Days calculation. With the Rare Water Tower and 5 days you would miss 5 Water if you harvest Greenhouse every day.
Depending on the amount of Gardens and with the mixing up of different harvest times it will get more tricky to optimize my own farm, but I like that part of calculation and optimization :)
With New Waxchester it will just become more diversified 😃
MY sheet for ROI with Seed costs: