Interesting and well calculated point Totenkopf, but the GDP defence spending is more reflective of national welfare policies than actual logistics. The Soviet and US defence procurement was roughly en par throughout the Cold War and where strategic and avionics development was concerned was higher in the US, backed by privatised contracting in an attempt to feed expenditure back into the economy.
Nevertheless US defence spending from the early 70's began relying heavily upon cost recovery programs. Every individual upgrade type was ridiculously expensive and ridiculously frequent.
The Soviets went the other road with downgraded exports instead of upgraded indigenous models. The total cost of the counter air defence and strategic air defence districts for example were still similar to the combined FX and LFX programs which produced the F-15, F-16 and F/A-18 fighters with a lower development cost, even though many more aircraft were procured by the Russians for the same cost. The problem was the Soviets didn't privatise and their economic system didn't allow for much in the way of cost recovery.
Where this gets muted is by the 90's, when Europe stopped buying American and the rest of the world got better Russian models cheaper. You can get a MiG-29A for the cost of an F-16A and according to the Luftwaffe it's as good as an F-16C Block 50 on any day of the week. That model is actually more expensive and has still been superseded by the newer Block 55 (which finally has a helmet designator).
Had the US spent as much of its GDP as the Soviets on defence budget, it is because of the capitalist economic system that it would've disentegrated long before the Soviets did. Money you spend on contracting, privatisation and social welfare support the Russians never needed to, the benefits were granted outside the standing economy.
Where the Soviets fell down was in empire. The US makes a trade partner and it creates industrialist opportunities whilst gradually infusing itself into the local political culture.
When the Russians did this, they invaded full scale on day one with the military, then took the new Satellite's welfare and resource concerns upon their own shoulders. Each of the Satellite states thus sapped Russian economics and resources rather than promoted industrialism and profiteering.
This is what has been mostly changed since the Soviet breakup, all CIS leaders are now essentially big time capitalist industrialists to the extent of organised crime bosses, or are insane nationalists fully halfway on the road to Hitler.
It's like having Al Capone win the war against organised crime in the thirties.
That period roughly 1988-98 marked phenonemal defence expenditure in the US for a political climate which no longer exists, with no chance of cost recovery, and it was cost recovery projections which governed defence spending at that time.
It is highly likely this was the primary reasoning for the Gulf War.