There are absolutely $599 laptops available from companies that aren't Apple but they've all made major compromises to get to that price in ways that people will notice.

The cooling will be terrible so that every 30 seconds the fans kick in at full speed, thermal throttling takes hold, and then it decides all is fine 30 seconds after that so you're working on a machine that's constantly cycling fan noise. The trackpad will suck, meaning you need to have a mouse precariously balanced somewhere anytime you're using it. It'll have some irritating BIOS feature you can't work out how to turn off that flashes a giant icon on the screen whenever you hit the caps-lock button. The casing will be plastic and snap where the screen hinges are screwed in after a year of light use. It may even be a Chromebook, making it a glorified tablet with an attached keyboard and (terrible) trackpad.

The thing Apple have done here isn't to release a $599 laptop, its to release a $599 laptop where the compromises are ones the average user buying a $599 laptop isn't going to notice everyday, while not compromising on the things they do notice. Its made of metal, the trackpad feels good to use, the keyboard is pleasant, and the battery is large enough that you're not carrying around a charger that weighs as much as the laptop itself.