2 is way too low, it should be "exponential", if possible, like 3 drones cost 5 perks, 4 cost 25, 5 cost 100, 6 costs 200 so on so forth, because that many bombers would be almost invincible, unless alo more than normal people scrambled. cuz 6 bombers would never get shot down by one/two people, unless the bomber sucks as a gunner.