Anyone with a gaming laptop - I can get dell laptops 40% off - so I was debating between a 7000 series 15 or 17 inch w 5th gen i7. But I looked at an alienware, but it's more expensive yet is a 4th gen i5. Is the major differentiator the graphics card that makes it more expensive?
There are many other plausible factors. Portability, battery, processor etc. all can affect the price greatly. However, Alienware computers generally are marked up more than your average brand due to the 'name' of the brand.
Alienware is often marked up for name brand. Though they do occasionally have sales that aren't bad. Though the X51 was personally the only Alienware I thought was a decent deal with a sale.