The cost of shooting down a missile or stealth aircraft far exceeds the cost of the offensive missile or aircraft. They “may have” a system that can do this but I rather doubt it.
Let them build all they want as it will deplete the monies for offensive weapons. We must simply build more offensive weapons which will again make the Soviet Union bankrupt if they try to counter them. That is what the great Ronald Reagan did, and the Soviet Union collapsed due to economics.
The winners in war are determined by industrial and economic might and a will to confront evil.
The gross domestic product of Russia today is about the same as Italy. Italy has but a fraction of the population of Russia. Russia can never win unless we permit them to win.
Forgot to add this:
Relative to industrial capacity one must always remember the civil war of the United States.
The South had the superior army and soldiers and achieved great victory at the beginning of the war. The North had great industrial capacity to make the tools of war and a good railway system. The North also had a superior navy and was able to blockade the South from help from Europe. That is why the North won and the South lost. The inferior army of the North won due to industry of the North and a superior navy.