I dont think you understood my ask. In D3 resource cost reduction impacted things like weapon throw+boulder toss and meteor+star pact. both consumed all remaining resources to boost damge per resource spent. RCR of 20% when casting with 100 was treated as 120 resource. Im curious if d4 does the same.
i understood it fine.
the serpitine, aspect does not because its doesnt take account cost.
as mentioned by someone else, kelpe(as do aspects/item that say "instead/or max/etc") does as it mentions must have max vigor aka a cost, which i thought my explanation made clear, but you proved me wrong.
serpitine has no "cost" to use its effects