I think a cheaper method might be to deploy thousands of drones each only carrying one or two munitions. From there you simply pile on more drones than the defenses can hope to shoot down. Since they are drones and you don't have to worry about losing expensive aircrew you can also have them fly at much lower altitudes when passing AA emplacements, making for a smaller window of opportunity for the AA systems.
The obvious problems I can see with this strategy though would be first, that guided munitions might need a lot of altitude to get on target properly, which might require rapid changes in altitude that the drones couldn't accomplish. Secondly the command and control system and subsystems would have to be very strong to handle thousands of drones, if not tens of thousands, and each drone would have to have some kind of inertial guidance system to guide it onto target in case command and control is taken out or jammed.
Even with those challenges though I'd wager it'd be cheaper than a small fleet of full size manned aircraft.