Anyway, my case for fireballs versus long range cannons. I'm starting with a straight comparison.
Long range cannons+ Same prevalence as fireballs (limited by apprentices)
+ Non-magical projectile (not stoppable by anti magic)
+ Penetrating projectile (cannonballs will bounce through enemy lines)
+ Rapid fire rate
- Limited Ammunition
- Mechanically unreliable
Fireball+ Same prevalence as cannons ( but limited by apprentices only)
+ Splash damage that can destroy entire squad
+ Will start fires
- Magical projectile (not stoppable by current enemy countermeasures, but new ones could be designed)
Let's also think about what they have to do. At extra long range, we need to blow up ships and Ballistae. A cannon shot against the ship will kill a dozen men with splintering, but will leave the vessel otherwise intact. A fireball shot at a ship will set the rigging on fire, allowing our vessels to close in for the dead blow.
Same for the ballistae. A cannon ball needs a direct hit, else the ball will just pass straight on. A fireball will set the surroundings on fire and destroy their entire battery. (They will place their ballistae close together, so that 1 mage can aid them all).
Cannons have their use against Moskurg's dense formations. There, the cannon ball can bounce through a dozen men, ruining any teamwork and striking fear into their hearts. At this medium range, the rapid fire will heavily disrupt the enemy formation just before the fighting happens.
My only fear is that the Moskurgians manage to make a counter to our fireball. They can not predict the cannon.
I also thought it went cheap>normal>expensive>very expensive>national effort.
That didn't seem to be the case when I was looking through the combat engine though, so I just rolled with it.
So, just to be certain, is the current system
cheap>normal>expensive>very expensive>national effort
or
cheap/normal>expensive>very expensive>national effort