There's a concept that people seem to not understand that is nonetheless important for balance, so I will elaborate on it slightly here.
Essentially, an attack by one player can threaten many.
The best example of this is nukes. Every player generally has their own base, and nukes threaten bases. For a team of, say, five people to successfully defend against a nuke, all five need a an anti-nuke. Anti-nukes are half the cost, but because so many of them are needed to defend against a single attacker, it's actually not very cost efficient to defend via nukes, as you would need 250% of the attacker's inputted resources to successfully prevent a strike by the attacker's nuke.
The same applies to other strategic weapons, such as Tech 3 and Experimental Artillery. Although a single base can be protected from a mavor by less than a mavor's mass in shields, five bases cannot.
Although one ACU can be mass-efficiently defended from mercies by UEF Tech 2 shields (600 mass in shields stops 1200 mass in mercies), five ACUs would require 3000 mass in shields to defend against 1200 mass in mercies.
This is an essential point to consider in making balance determinations.