Huh, I guess either ATB got an update or most of my users haven't used ATB, if there are issues like these. (Truth is, my own project uses CTB.)
One way for a dualtech to have a "unique cost", as you put it, is to have a dualtech be its own "component" for at least one of the actors involved. (Exactly one, if you're using Party Limit Gauge, because it's a shared pool.)
(There are other solutions, but they would require edits to the plugin itself, and they would not be quick fixes.)