Whereas I have been around the block a couple of times

the 1/6th size was introduced WAY BACK....in the '70's if not before (was it a Berkley kit redone???) and is/was die crunched. The 1/5th scale is lazer cut which might make it a bit costly to manufacturer (plus it has some good engineering in it)...the 1/4th I don't have a clue - LOTS of wood (die crunched???).
As always, I could be wrong!