▁- 6 0 0 ▁cargo ▁variant ▁with ▁ 3 0 ▁firm ▁orders ▁plus ▁ 2 0 ▁options , ▁in ▁a ▁fre ighter ▁configuration ▁from ▁the ▁factory . ▁ ▁As ▁of ▁September ▁ 2 0 1 8 , ▁ 1 8 7 ▁early ▁variants ▁had ▁been ▁produced ▁with ▁ 1 7 2 ▁operated ▁by ▁ 5 5 ▁carri ers , ▁ 3 6 5 ▁- 5 0 0 s ▁were ▁delivered ▁with ▁more ▁than ▁ 3 5 0 ▁in ▁service ▁at ▁ 7 5 ▁operators , ▁ 4 4 4 ▁- 6 0 0 s ▁were ▁produced ▁and ▁are ▁operated ▁by ▁ 7 4 ▁carri ers ▁with ▁a ▁back log ▁of ▁ ▁orders . ▁By ▁then , ▁with ▁more ▁than ▁ 6 0 ▁- 5 0 0 s ▁and ▁ 4 0 ▁- 6 0 0 s ▁in ▁storage , ▁new ▁aircraft ▁le ases ▁fell ▁to ▁$ 1 3 0 , 0 0 0 ▁per ▁month ▁from ▁$ 1 7 0 , 0 0 0 . ▁The ▁- 6 0 0 ▁list ▁price ▁of ▁$ 2 6 . 8 M ▁is ▁typically ▁disc ount ed ▁by ▁ 2 5 % ▁for ▁a ▁$ M ▁value , ▁a ▁ 2 0 1 2 ▁aircraft ▁is ▁val ued ▁$ 1 3 . 3 M ▁and ▁le ased ▁$ 1 1 5 , 0 0 0 , ▁falling ▁to ▁$ 1 0 . 2 M ▁and ▁$ 1 0 0 , 0 0 0 ▁ ▁in ▁ 2 0 2 1 , ▁a ▁D ▁check ▁costs ▁$