One of the selling points for the U.S. F-15 fighter is its combat record. F-15's have, in 30 years of existence, shot down 101 enemy aircraft. No F-15s have been lost in combat. Typically, a new weapon is a hard sell, until it has been in combat, and survived (reputation-wise). When a weapon has been in combat many times, and done well, you can usually sell it at a premium. Such is the case with American warplanes, when they are competing with, say, Russian model.
But in some categories of weapons, the Russians have the winners edge. For basic stuff, like rifles (like the AK line), mortars, grenades and so on, the Russians have a well-deserved reputation for ruggedness, reliability and low price that helps move the goods. But for high tech, warriors still look West.