From what I know yes they are. The most important part is that Alienware's laptops have superior video cards which is an essential component for gaming. But honestly I don't know much about gaming laptop I don't know if you can get the same specs for cheaper elsewhere. I noticed you can get a laptop with similar CPU, RAM and SSD for a whole lot less, but the problem is always the video card... But maybe someone with more experience with gaming laptop could chime in.
But actually, RAM and SSD are upgradeable in laptops without voiding the warranty