Sony and Microsoft sold there Ps3 and Xbox360's at a loss as all the money is in software sales. If enough people will buy the headset then they could sell at a loss and make more through Software sales than they ever would through hardware. At this moment the market is not big enough for them to lose money on headset's. That's the way i see it anyway. At the current price VR will not take off.
Those consoles were only sold at a loss in the beginning. The plan is to always regain profitability over time through economy of scale.
But yes, they ultimately rely more on the other aspects - the ecosystem as a whole. It isn't just software, it's accessories, subscriptions, even merchandise(usually franchise-related), but also software.
Problem is - VR doesn't even have a small fraction of the ecosystem userbase that console manufacturers rely on. You can take the console approach when you can be relatively confident of selling tens of millions units over a year or two, while having hundreds of titles available that you're taking a cut on, and also the accessory sales and now the common online subscription costs.
VR has none of that. NONE of it. So you're entirely right - at the moment, VR does not have the market to do the same sort of thing. Oculus are playing the long game and trying to build up to that. It may or may not work, though I do think that the cost of their headset probably includes some margin for R&D expenditures rather than just being 'at cost' for materials. The Vive has to be sold at a profit because HTC does not have a software ecosystem to make money off of. And Valve make money no matter what, because they dont have to spend any money on making or selling the headsets, they just hope people buy them and come to Steam to buy software. They'll be fine whether VR fails or not, though.
Anyways, point is - cutting $100-150 off the entry price of a VR-capable GPU is not going to initiate a giant surge of VR buyers. Those that are price conscious will mostly not find the idea of a $600-800+ VR setup appealing in the first place. Meaning that it's going to be hard for the costs of VR headsets to come down anytime soon, and sustaining the high price barrier to VR no matter how cheap GPU's get.