The cost of an incremental commit. The cost to develop and interface. Systems with higher conceptual complexity require greater investment to understand.
H: Conceptual complexity is proportional to the cardinality of failure cases.
"The fourth lesson: Multi GPU (SLI/CrossfireX) is fucking complicated. You cannot begin to conceive of the number of failure cases that are involved until you see them in person. I suspect that more than half of the total software effort within the IHVs is dedicated strictly to making multi-GPU setups work with existing games"