Most business travelers don't actually travel business class. And don't get to pick premium levels of service. And that would be even less the case if those premium levels were at a premium over today's premium levels.
For US and European carriers, it's around 75%. Since the cost is 4 - 7x higher than commercial, most people aren't paying for this expensive personally. Not sure about other industries, but for consulting and tech, the standard is to allow a business upgrade on international flights and not domestic.