That is what the people who started most wars thought, yes.
I mean, that's the core concept of communication theory in war. that asymmetrical and/or limited information made one side of a dispute overstatement their chance of victory. (e.g, both sides thought they would win, but one has to be wrong.)
how I see what's happening is that we are at stage one: grievance and threat of retaliation.
Marienburg has a grievance with the new Chanel and is threatening embargo as retaliation. (they have estimated that their chance of winning this dispute to be high, as the empire is stretched thin and their navy is better than the imperial navy.)
stage two: the empire does its own calculations and responses: this is where the empire is at and why our Bismarck Expy is asking what the dwarfs will do.
-- if the dwarfs are expected to do nothing, then Marienburg is right in their estimations.
-- but if the dwarfs are expected to act, then the empire has information that Marienburg does not and can recalculate their chance of winning the dispute.
stage: 3 the Empires response: this is the point the empire shows their cards, that the dwarfs will support the empire in the dispute (gunboat or economic) and Marienburg has to re-estimate their chances of winning the dispute.
problem with the economic option in a premodern viewpoint (the characters don't think with modern views like internationalism or free market, but in international realism and mercantilism) comes around here, as it gives Marienburg the initiative.
they get to decide the best response.
they think the empire cant last the 5 years? then they wait it out.
they do think the empire can last the 5 years? then they can respond.
-- give up?
-- increase the pressure?
-- make more deals to get the elfs to pick a side
-- attack the channel?
-- Attack
barak varr ( the most extreme, but possible if they feel that threatened.)
it gives them the initiative.
Gunboat on the other hand, while a risk, is a calculated one to jump the stages passed 3 and to stage 4: sabler rattling. (the empire threats them back with the support of the dwarfs.)
create a pressure point were Marienburg has to make a binary decision before they can re-assess their chances. to back down or hold ground.
this is to help initiative on the empire's side and to keep Marienburg at the table, as the fight is now a lot more scary then they though it would be and so are less committed to calling the bluff. stage 5: war
I'm not saying this is right or not, But this is generally how international disputes were thought as by the acters in early modern times, which the empire and Marienburg are kind of based off.
that the threat of gunboat retaliation was better than economic retaliation because it kept the other side off their toes.