Linux has a long history on Macs, and Apple directly contribute to a number of open source projects they have benefited from over the years. So the question seems a bit odd to me.
Let's put it this way OP: OSX is a Unix fork running on bog standard Intel hardware these days, with a UEFI for bios. They get it from the same bulk suppliers as everyone else in the industry. Software, casing and marketing terminology is what differs. Hence the 'holistic experience' commands a premium from Apple's point of view.
But considering your requirement for build quality, probably battery life and other selling points of MacBooks, I doubt you will save that much cash by going elsewhere, unless you buy without an OS or second hand / outlet. If you are a student or know someone who is, it can help, as discounts from both Apple and traditional PC manufacturers are good for that demographic.
Whether you want to keep OSX, dual or triple boot is up to you, though. As a user there is nothing stopping you at the moment. Mind, with the way Microsoft is trying to exploit secure boot module of UEFI, I wonder if Apple will follow suit? Still, virtualization is always an option!