By your definition a KT would not be a hard counter to a rifle squad because it costs way more in relationship to the rifle - this is a stupid metric definition. If a unit or ability can easily wipe another unit, it is a hard counter regardless of cost.
can riflemen damage/kill a VI B? not significantly (just in case i actually need to say it: AT RG is not significant); therefore the VI B hardcounters rifles.
if you want to be more technical about it then compare roughly the same resource amount of rifles with VI Bs. again, it's not about cost it's about
performance to cost in specific matchups. to use the AT gun example
again a flanked AT gun doesn't do shit to a vehicle despite being a hardcounter to vehicles.