Generally costs increase with size and manufacturing complexity. A design, which includes cutting into the shaft and/or hub, weakens them and often involves increasing the size of these major components beyond that necessary to transmit the loads. This not only increases the cost of the shaft but all associated components will be larger and more costly. In addition, it should be remembered that larger diameter gears have larger bore sizes and so require larger shafts and possibly bearings. This adds further to the overall cost.