I'm with Thomas_Lord... IBM's PC division took a radically open stance with the PC market. I remember being astonished to see the circuit diagrams in the IBM 5150 Technical Reference manual, but understood the point to be that IBM wanted to make it easy to build compatible hardware and software. They reversed their stance - and lost their leadership - with the second-generation MicroChannel and PCjr architectures, largely due to the profit margin problem you identify.