A third party manufacture has licensed Mac OS before... it sucked. I can only imagine how shitty OSX would run if you had HP trying to make a bunch of 450$ desktops preconfigured with OSX, and was built to a profit margin (ie: machine probably only cost them 100 less than that). The only real market, realistically speaking for OSX on a machine other than apple's would be in the "I can't afford shit , so gona see what the cheapest thing is down at best buy" market. since anything else isn't going to be a big enough market share.
Also apple is primarily a hardware company, so it makes sense to keep their best asset (the OS) on their hardware.
here's my annoyance though- a lot of the hackintosh community is OMG apple is expensive - here's my $800 build.
I don't want a $800 machine.
I have money sitting around for a mac pro that I can't buy because apple doesn't update it. Fine. I'll GLADLY pay $3k for a comparable hexacore workstation from dell/hp, the included warranty is a benefit. I've built machines for years but I'm happy to pay the apple premium just to have something that works without fiddling. That said I'd also happily buy an alienware/dell/hp/etc if one of them was 'hackintosh friendly' and thus came with formal/informal support.
The hackintosh route is fine, however I don't particularly want to research/piece a build together. That's a waste of time/money just like spending $3300 on a 2.66ghz quad that's 18 months old from apple.
Other situation I'd be fine with: apple dropping the prices to reflect present day value, in which case I'd just buy a 8 core machine now at a discount and trade when needed. But this 'price is what it is on release day' a year and a half later is asinine, even for apple.