One has to be cautious of using the very earliest Lionel F3 shells (1948) as they were made of styrene plastic and capable of losing form. Not to mention paint did not stick as well (lots of 2333 NYCs have flaking paint).
Early MPC F3 shells were good quality and apparently dirt cheap. Trainland in NY sold repaints in postwar road names for $29 @, in the 80s. If you assume they made some money (of course), and the painter got paid , then the raw shells must have been little. They did lack the air vents in front and portholes but still a good starting point. (it is easy to spot bogus "post war" F3s which are lacking those front air vents).
