OK, so I don’t actually see an appreciable difference there.
Though I do appreciate as a staging site it likely is not under load, it does seem to suggest that perhaps it is an accumulation of many factors – including other plugins and your theme – that add to the overall load time and perhaps create something of a perfect storm.
Honestly, I’m not sure how much more we can do on this occasion since there’s no clear and obvious problem I can see in an otherwise clean environment that stems from the presence of Events Calendar PRO.
What do you think: do you still have concerns/a different view of things? Given your earlier note on the relative snappiness of the site for unauthenticated users it sounds like you may be less worried at this point?