Throwing weapons aren't more expensive than any other items in Strat, but the standard load out for a thrower, hybrid or not always requires 2 or more stacks of a throwing item, which makes it severely cost inefficient. That is, compared to your standard two hand hero, polearm or shielder. Maybe not expensive as cav, but generally not as efficient. Of course, Strat economy is different than the upkeep system where you can't pay for the same item multiple times in a round, but in Strat you pay for all 2-4 stacks no matter what.
The solution would be to lower the price of throwing, of course. Then consider raising the price of bows and crossbows, but lowering the price of the ammo,