Adobe were the breakthrough company to develop video editing on Mac, with what is now Premiere. Final Cut was a spinoff of that when the developer left for Macromedia, which was in turn split between Apple and Adobe (FC & Flash, respectively): http://steveblank.com/2009/05/11/supermac-war-story-x-the-vi...

Now you're right about Apple's price cutting, and it's more obvious how this drove down the cost of video - but on the music side while you had ProTools at the extreme high end and Logic at the prosumer price, over on the (post-Atari) PC side you had very aggressive competition from Steinberg (Cubase), then Cakewalk, and ultimately a host of others - not to mention trackers. eMagic had a big first-mover advantage in their price space, but competitors were really eroding that with a combination of pricing and ease-of-use. I personally think EMagic would have gone bust within 2 years if they hadn't been able to fall into Apple's arms.

To be fair to Apple, they were very smart to focus on things like high bus bandwidth and high-resolution hardware timers which are de rigeur for this sort of work. Wintel was able to play catch-up in large part because of the rise of electronic music, where things like hardware latency and so forth were less critical.