Actually Macs are not that expensive, take an intel motherboard, put quality components on it, a nice video card, a glass protected high definition monitor (if iMac) and you aren't very far from the price of a Mac. You can buy an EEEEEEE machine or some other such cr@p for less, but you get what you pay for...
Apple today has more third party hardware than Amiga could have dreamed about when the company was alive, you can't buy Apple clone Motherboards, but you couldn't buy Amiga clone motherboards either. Most Amiga users never open their computer boxes back then, the idea of stretching the hardware came about the time of the death of the company.
My original Amiga 1000 and 2000 cost substantially more than a generic PC back in the day, folks at work thought I was stupid for dropping a large wad of cash on a non-compatible machine.
Yes, OS X is based on BSD (not Linux), my point is that Apple was able to make that vchange because they are Apple, they define what Apple is and what Apple isn't. The AMiga lack such leadership, and so can't really enter the 21st Century technology wise.
Finally drivers, unless you are talking about AROS hosed on Linux or UAE, Linux drivers have little meaning to Amiga, you can't use Linux drivers on AROS or AmigaDos directly.