Bar action locks, or those with main springs ahead of the tumbler, predate back actions. For instance, flintlocks were almost always front action. Percussion locks were a mix of the two but tradition and general preference favored the front action. In breechloaders the front action was seen as leaving more wood in the wrist for strength. Back actions were favored by some, reasoning that it left more metal in the breech area for greater strength in that area and also allowed a sleeker action. The debate was never settled and each had its own adherents. I doubt there was any significant difference in cost of production. The back action does allow for a longer main spring and therefore somewhat smoother movement.
