Every operation will need SP for bandwidth (resource credits). Creating and managing SMTs will involve operations, which will require credits. The resource credit system should make it somewhat more transparent (if still somewhat complicated) to know how much is required as a function of the resources used by the operation and the availability of those resources on the system.
Also, it will remain the case (as with bandwidth today) that the resource credits needed will vary according to system usage. There is not a fixed amount, although in theory there should be a cap (very high).