The M43/MFT Shaft !

Not true.

Silicon components are made from slices of silicon rods. Because of certain phyics of manufacturing these rods max out at about 6-8 inches in diameter. That means the larger the sensor the fewer sensors can be produced from each slice. As the size of the sensor increases, the yield per slice drops like an anvil tossed off a bridge. Cost per sensor skyrockets. Doubling the sensor size drives up the cost by WAY more than double. Way more. It is a matter of basic geometry.