There's a big difference between a laptop and this PC... namely the battery system. Instead of capping framerates on battery, the VR GO pushes max juice to the components at all times so that you can get the 90 FPS most VR games aim for.
An advanced user could probably figure out how to configure a laptop's OS to let the PC operate with the lid closed and uncap frames on battery (which will drain the battery even faster), but check out some of our reviews and see how long some of these laptops run with Battery Boost enabled. You barely get over an hour in most cases, with some giving an hour and a half. But that's without full-throttle graphics performance. A typical sub-$2,000 laptop can't hang in this manner. Furthermore, cooling becomes an issue if you stuff a laptop into a regular backpack, and it would probably throttle like crazy.
This product was designed for VR specifically. There's no need for the user to alter OS settings or disable battery-saving features, they can just unpack and GO (pun intended). Everything about it was designed for it to be on your back without a fuss.
I can see your point (there are equally-powerful or more-powerful laptops for less), but it's like comparing a tractor to a car because they both have engines. Each device has a specific purpose, and the VR GO's purpose is to immerse yourself even further in VR.