Shotone
I believe the 4 million rough cost is from IOT to Wings ( maybe completion of first OCU)
When you factor in recruitment costs, Officer training costs, hold, medical, dental, accommodation, pilot training etc etc it does add up very quickly!!!!
Each OCU does obviously cost money, there's no getting away from that.
But simply, if you get 20+ years out of one initial recruitment and training cost, that's alot more cost effective.
Not to mention the experience that's retained, and thus safety.