I suspect Desk-pilot has it right.
It is more than likely it is the salaries ( going forward) that the Beanies wish to save a bob on, by getting rid of the most expensive pilots, highly unlikely it has much to do with training costs.
Perhaps this is strictly essential, but I doubt it. I have had conversations in the past with those more intimately acquianted with the black art of costs & accountancy than I am, it has usually been revealed to me that wage costs are relatively unimportant in an airline in the grand scheme of things. If they truly are so desparate to reduce these, I would suggest you are already up sh1t creek minus a prop blade.
I would wager that pure corporate greed, manifested in someone seeing a way to make an extra buck on the premise of "survival methods", will be closer to the truth here.