Yes, Russia’s defense budget is relatively small, but military quality is not a direct “dollar for dollar” comparison.
25 years after the collapse of the Soviet Union, Russian engineers are still producing advanced fighter-jets, for example. Are theirs equal to the F-35? Doubtful, but they also aren’t paying their military-industrial government cronies $125 million per copy of their fighters, while we are.
You are correct, however one must always consider the following: The most robust missile defense system will not stop all the missiles be they American or Russian. Both sides will suffer devastating damage that will probably render both a no longer functioning nation state. It also costs a lot more to shoot down a missile than to build an offensive missile. The old paradigm of Mutually Assured Destruction existed in 1960 and it exists today.
If Russia and the West get in a new arms race the West due to economic power will win. We can build them faster and in greater numbers than Russia. However, some Russian warheads would get through and cause great harm. Most of our warheads would get through and Russia would cease to exist.
Putin is a real Son of a Bi-ch. He will never attack us in a nuclear war as we will not attack him.