You don't have to get the earlier tier/level silencers to get to level 3. Ergo it isn't 8 points just to get tier 4 silencer, it's just 2 points.You need to reset, stop putting points to tier 1, 2, and 3 silencer/scope.
MK1 + silencer + scope should only be 12 + 2 + 2 = 16.