The exo evaporated to three armored warheads mkIII.
I'm not sure I would consider 9 AIP a fair trade for just killing an Exowave, unless the alternative was losing. The exo will be back in an hour, but your AIP won't have gone back down.
I suggest:
Lighting warheads and martyrs get a limit on the amount of damage they can do to a single unit:
Warheads at 10 million/mark
Martyrs at 5 million/mark
Armored warheads should retain their ability to hit big things, but be very costly:
AIP cost to 3/mark
Metal to 1 million/mark
And total damage for all of them should probably be halved.
Capping warheads at 10M/mark means a max of 30M to a signle target - better than nothing, but not all that useful against starships or other big targets.
If you were putting a cap in, I'd suggest something more like 100,000,000 flat for all marks. Enough to kill almost anything, but still capped so stuff like Golems can sometimes survive.
I also see no reason why the Armored AIP should triple. If you wiped out an entire exo with 3 Mk III Armoreds, you could have done it just as easily with 3 Mk III normal Warheads. I have no idea what the cost was supposed to be - besides "not 1".