It's not just royalty costs. If that were the problem, anyone could make a BD player for Mac OS X and just pass on that cost.
The problem, I've read, is that the media companies blocked licensing for computers due to piracy concerned. They made many demands of Windows that resulted in changes throughout the system, including drivers. Basically their demand was that the data never be sent in the clear on certain buses and that a deep-level process would be looking out for anything trying to intercept the data. Microsoft made these accommodations throughout Windows to the satisfaction of the studios.
The same article theorized that it would be impossible to meet the same studio requirements in an open operating system, so that we'd never, ever see BD licenses for a Linux player.
So in OS X we'll never see a licensed BD player for playing protected content. There are perhaps three reasons for this. One, it might be impossible because the Darwin kernel is open. Two, even if it isn't impossible, Apple probably has zero interest in making the accommodations that the studios demand. Blu-rays compete directly with the iTunes media store and possibly also the iCloud. Three, Apple is probably planning on getting rid of the optical drive from its entire line of Macs some day; adding Blu-ray directly conflicts with that.
If Blu-rays were a spectacular success story, Apple might have to concede. But optical media sales are on the decline so there is little to no pressure on them for BD playback. The people who really, really, really care have already found workarounds.
