Rocket count is useful only when it describes a route. A strong armored panel beside a cheaper door path does not increase the practical raid cost.
Measure required layers
Count only the walls and doors a raider must break to reach the protected room.
Upgrade the bottleneck
Spend stronger materials on the cheapest mandatory layer before hardening panels that can be ignored.
Check more than rockets
C4, satchels, and explosive ammunition can change the farm bill even when the familiar comparison uses rockets.