Perspective from a computational biologist: Campus hosted HPC means the direct cost pressure is seen as IT staff and hardware related costs. Researchers are encouraged to use the available capacity. This is good.
Externally-hosted HPC means every single compute job is seen as something that directly costs money. This negatively affects the quality of scientific output (research playfulness / creativity / focus on the research / etc).
Yes. The costing models that are used (and often required by granting agencies) make apples to apples cost comparisons almost impossible, and impose undoubted and significant false costs on research budgets. No question this is true.
Externally-hosted HPC means every single compute job is seen as something that directly costs money. This negatively affects the quality of scientific output (research playfulness / creativity / focus on the research / etc).