Probably a faction thing, as the other duke seems to be good at manipulating the lower nobles. And the deal was to sell the carts at the price that of half a mine cart for 5 years, which would probably be operating at a loss.
If he got the trade monopoly on rails and carts, his territory could have become wealthier than the royal capital, as a part of the deal was the trains having to depart from his territory as a central hub. If you are the intersection of people and goods people will spend and trade in your territory.
What the merchant is doing is called overbidding.
Cornering the Supply, starving the Competition and when rivals are eliminated, you dictate both the buying and selling prices. I do not know where the girls got their ideas from...
So the green tea birch got a real green tea bitch inhabiting her, and a dumb one at that. Well our Villainess got life on easy street now if only she wasn't so fucking timid.
It shows that the Japanese are ignorant about slaves, they cost more than an employee... you need to feed them, make sure they are healthy so they can do the work in the first place, shelter them and make sure they actually stay. An employee you just give a salary and let themselves figure out...
Wow the quality of the work, is all over the place (not the translation), columns are copied pasted, some environments are photo bashed and the characters are hand drawn so sloppily lol it's been a while since i read this, and wow.