So I take it that you can't actually explain why a cheaper unit should defeat a more expensive unit then?
If you don't see why yourself, you should be here, not in balance section, asking people to explain you basic mechanics.
Post a thread there asking for help with that and I'll gladly explain it to you there.
And if you really insist its still a balance issue, then post a thread about ATGs being OP against tanks and I will again, gladly explain why you are wrong there after half a dozen people will ridicule you.