so, being slightly cynical, they'll pass on the older Block 3s as they start because coming maintenance intensive, meaning they'll be able to concentrate their cash and manpower keeping the Block 4/5s etc serviceable and at sea. But the sale price should be much lower as a result.
Sort of like why old Jaguars and Mercedes go at such low second hand prices. Great cars - but the running costs can be crippling if something breaks so you have to factor it into the price you pay.