I think the problem is more your understanding of medieval and renaissance economy than undead.
There is another problem with using undead, especially ones enthralled by Create Undead. How general can the commands you give them be? Sure you can order them to harvest all the fields they have sown, but does that involve also the threshing and all the other steps needed to make the grain ready for milling? Does the order to mill the grain also include filling sacks with flour and storing them in your granary?
So the one casting create undead every day must also know a lot about agriculture to give the correct commands.
I am unfamiliar with them. I will look into them.
Edit: From what I read the increased income was not because the land was used more efficently or for some higher paying product, but because by law the people the serfs were replaced with had to pay higher rent.
Apart from ancient Egypt and Japan with their Koku I know of no place where food was used as actual wealth. Sure, you were wealthy if you had enough food, but commercially food was of limited value. It was hard to transport in bulk and temporary as it rots away. So when you have enough food more of it is of little value which is why nobility wanted farmers to join the coin based economy to tax them in coin instead of food (actually they were paying rent, not taxes)
Often taxing in coin came first and thus forcing the serfs to earn coin in some way.
Trade of food was very limited. The amount of food you could preserve was low as it required special crops or other items that were only produced in low quantities. Also, don't confuse modern conservation methods with what was available in the middle ages. Without air tight containers sauerkraut can't be stored for years.
Most food in the western world like grain rotted away over a single year making long term storage in meaningful quantities impossible.
Transportation was another issue as food are bulk goods unless we are talking about luxury goods for the elite. Thus only doable with access to rivers and the ocean for both the source and destination and because of the criticality of food when you need it it required safe trade routes. Thus large scale food trade was not usually done by merchants but by the state which ordered the transportation of it. See how Rome was fed by Egyptian grain.
Food was taken when nothing else was available, but it was a hassle for the nobles once their stores were filled because transporting it was problematic and you had trouble dividing it in the case of livestock. So whenever possible taxes were taken in coin, produced goods or labour.
No, the economy was not food based. Food was not money. Growing food was a necessity and was mostly done for the farmers own need plus a little bit extra to give away or trade for coin so you could pay taxes (most villages had a closed economy which dependent on sharing with those in need with the expectation that this was repaid in kind of you are needing something)
Not really as food is not wealth when you have much more than you need. You usually can't trade it away in bulk, people will not work only for food so its on its own not enough for payment for specialists and it rots away.
Some reads:
Thanks to our helpful volunteer narrator, this entire post series is now also available in audio format! As the fourth and final part (I, II, III) of our look at the basic structure of food product…
acoup.blog
This week and next, we’re going to look at an issue not of battles, but of settings: pre-modern cities – particularly the trope of the city, town or castle set out all alone in the midd…
acoup.blog
Back to the excel
For fun I did a calculation for a "science fantasy" setting with a modest 4 billion and "only" a 70% specialist rate. The results were interesting with thousands of level 18+ characters and millions of level 5s.
Most people who write science fantasy fail to comprehend the sheer scale even a single earth like planet has, let alone multiple ones.
Now imagine how many high level characters a planet like Coruscant with a population of trillions according to some star wars books would have.