I dont understand your terminology. Usually cost effective means that a unit is very effective for the amount you pay- thus it is cost efficient. You seem to view the terms "cost effective" and "cost efficient" as having different meanings, please explain.
Sure, both words (efficient, effective) seem pretty similar but they are not. Both are aimed towards a process and its results.
Effectivity is how well a job is done. If we are talking about a shooting range, a sniper rifle will almost always hit where you aim, also as dead center as possible.
Efficiency is how certain you are from getting the job done, also with the less amount of effort. I.e. A shotgun if we keep on the previous example. A single pellet hitting the target should do.
A cost-efficient unit is one that mostly trades resources, you might loose a tank in a 2v1 but both tanks you had were less expensive than the other one you were facing.
A Cost-effective unit is one that ensures you the job done, a sniper killing models is one of the best examples. Since the game has flanks, FoW and complex cover mechanics, units are indeed more or less effective at specific tasks. (AI/AT/preservation/mobility)
Thats why there are endless discussions of Squad1 vs Squad2 in the balance forums, people dont realize that unit have multiple tasks to perform and different effectivities at each one. But because unit preservation is paramount in CoH2 the cost-efficient units are often, but not limited to, the hard counters like TD vs Heavy Tanks