The difference between something like the Rift or the Vive and mobile-based stuff like Gear are huge when you get down to actually using it. Even discounting the differences between Rift and Vive regarding how they track motion, the Gear doesn't even have positional head tracking, just orientation.
In use, this makes a huge difference if you're looking to put someone in a virtual environment. It's not even restricted to gaming applications. All of the software I've tried on my Rift dev unit and someone else's Gear made this abundantly clear to me. Not being able to lean forward/back/around things takes away a huge part of the "immersion" factor leaving you with more of a souped-up 3d screen.
In terms of cost, for the Gear, don't you also need one of a few specific, expensive Samsung phones? I admit I haven't followed it as much lately so I don't know if they are selling something more affordable with the phone-stuff integrated or allowing the use of other phones. When I looked last, you needed a ~$700 phone plus the Gear. Not too big a price difference between $800 for phone+Gear and $1000 for a good video card+Rift. Personally, when I'm even considering something this expensive, new, and unnecessary, $800+ versus $1000 isn't a huge difference since I'm already spending a lot on something I don't really need.
The other huge thing I've noticed is that all of the best new and in-development VR stuff just isn't gonna be something you can run on a phone or a Playstation. It's gonna be beta software (if you're lucky) and require a powerful, flexible platform like a computer. Down the line it will even out but right now, none of the really impressive stuff I've seen for VR will run on Gear and I doubt it will be in the Sony Playstation store anytime soon. That same console-level polish and ease comes with a flip-side: no access to anything that isn't seamless or marketable just yet.