It would be harder if the quantities involved were much larger. Your
rival might not be able to meet all the demand, or afford all that is
for sale. Also, to keep his place in the queue costs a noble forever
stuck in one place. Noble points are less easy to get than they used to be;
that's quite a sacrifice so I'm happy for it to have a reward.
Anyway, you could
1) Move somewhere else; beat _him_ to a trade route.
2) Undercut his price; the city will then trade with you instead.
3) Negotiate. Offer to pay him to limit his trading. Offer him access
to a city you have sewn-up in a similar way. Turn up with soldiers
and 'invite' him to limit his trading. If the noble isn't oath loyalty -
bribe him to your side!
4) Pay a warlord-type player to take care of him for you. Attack that noble,
or the couriers that supply him.
Trading _should_ be cutthroat to some degree.
> (now if you had about 6 nobles selling goods that would almost be a
Achieving a _local_ monopoly is a good ambition for a trader. Don't worry;
it's a huge world. No one player will monopolise all of it. (THAT's
what traders guilds or alliances are for....!).