Inkless Ehh, once again, comparizon of PD and missiles has no sense, you should compare PD vs Shields vs Armour as defensive parts,
And you have to compare Misilles with other weapons.
Complaining about price of PD vs Missiles really does not make any sense.
Second, i show you example of missiles and PD comparison just for you to understand difference between them.
And yes PD played crucial role in defending ship, but from exact size ( you are one i remeber for building huge missile ships) was even full PD ship nt enough to stop all missiles.
Now, PD are not crucial for missile defense armour , shield and destroying missile ships is the way.
BattleCruiserCommander I did test PD efficiens (14.0) and 8 Pd vs 1 misile launcher hold missiles for 4 minutes, videos from 2/4/6/8 PD vs missiles will be here soon.
So this number are pure teory, no one build ships without armour, shields and so on
8 pd = 8000 + 1 reactor = 15000 + 10 crewmembers to keep then energized = 34 000 credits.
Than you must have control room, thrusters, another reactor for thrusters because 1 reactor is just enough to feed 8 pd, and you came to to ships which cost like 60-65K
1 missile launcher + 1 factory + 12 crew = 40 000 credits
Than you must have 1 control room, some thrusters and you came to ship which cost 60-65K and always beat same price PD only ship.