The total cost for materials per box is about the same for any box used.
The total cost for box install and wiring path rough-in is $5-$10 less with Plastilock boxes. The total cost of the wiring rough-in is 20-30% less with Plastilock boxes. Plastilock boxes will meet Code, where "cut-in" wiring may or may not.**
Plastilock boxes and conduit will always provide a chase for future upgrades! **
* Install Time includes cutting foam for wiring runs and/or boxes, installing boxes,
attaching Romex, connectors or sweeps & conduit, depending on box type.
** Will meet code if metal box is properly secured, and wiring is securely attached inside "cut-in" foam channels at least 1" from finished foam surface.