I could see 100/100 being viable in extreme cases, such as that of a drought or other shortfall. If a duke is bankrupted in such a scenario, that is no problem. After all, the game isn't meant to be easy and predictable; the possibility of something going seriously wrong serves as an incentive for players to play better. Smart dukes could seek out ways to acquire additional food-producing regions, or levy more control over the market, in order to keep the cost of their food down. Incompetent dukes wouldn't do anything, and so they'd be forced into bankruptcy and possibly even starvation. Higher prices, better rewards and larger potential losses would lend more weight to trading and encourage a more meritocratic system than what we have now, which basically neither rewards merit nor punishes lack of it, leading to very apathetic gameplay, which a lot of people don't even bother with.
You are confusing competence with opportunity. Dukes don't decide who go to war, rulers do. Rulers don't decide how large they can expand, noble count do. There aren't always the nobles to acquire more food-producing regions, and often, there are no additional food-producing regions to be acquired. High gold prices are only fair if the need to pay them is rare. If you must buy food all the time, then it's another story. And if every city had to buy food at 50 gold per 100 bushels, I'm sure all of them would go bankrupt. I doubt any single city can, at full population, afford to buy all of their food at 50 gold per 100 bushels. Much less at 1 gold per bushel. In reality, though, you'd have a few realms with insane surpluses that'd have their lords sell to their cities for cheap, and every other realm on the continent would go rogue due to starvation. That's the scenario you propose.
Your magical thinking that dukes can simply work everything out if they work hard enough is utter bull!@#$. Incompetent dukes will starve more often no matter what, but no amount of competence with compensate for circumstance.
