Metro OT  

 While I have no stake in the Metro discussion, I'd ask you to consider this view as to producing revenue, in conjunction with your view of 'all others are just cost centers':

 Aircraft will always require maintenance; be it scheduled; unscheduled -as in chip light, instrument failure, etc; or unscheduled -as in medstaff ripped handheld radio cord from connector/ broke key off in door, or perhaps pilot put the TR into a fence.

 When maintenance is performed as a preventative item; or inspections & repairs are performed expeditiously and professionally, the aircraft downtime is minimized. This actually allows production of revenue. Sadly, yes, there are those though that want to be reactive instead - both maintainers & Management/Operators, which does cost potential revenue.