That's important to a business; not so much at home.
This is why I don't want people building their own PC, even though generally they can pick any tool they like: it shows they have the wrong priorities (at least for our team). Unless your job involves something really resource intensive, a high-end laptop (combined with external screens, keyboard and such) is more than good enough and much more practical.
Don't get me wrong, I love building my own machine, I build my own home server from scratch just for the hell of it every few years.
But simply the fact that you call it "half as expensive" suggests you have no realistic idea of actual costs. The time you spend searching the parts together is already more expensive than a MacBook.