Originally Posted by
B747-437B
The different types of 3-abreast seats are not interchangeable.
Left aisle, right aisle and center section seats are different part numbers and cannot be swapped. So there really isn't a significant economy of scale due to that.
The different seat sections have different part numbers, but there are multiple parts within these which are common. There would be less of these common parts if there were sets of 4 and 2 as well.