I agree it seems overly simplified to the point of being useless. A single Columbia class submarine (without munitions) costs the same as (approx) 10 million lo

I agree it seems overly simplified to the point of being useless. A single Columbia class submarine (without munitions) costs the same as (approx) 10 million loaded AK47's. The two of these would have very different effects on peace, especially not considering where those AK47's are used. World GDP also doesn't account for purchase parity. A state with cheaper labour building the exact same weapon as a state with more expensive labour would still result in the same weapon being created.