My personal experience has been that my VR development PC, which cost me around $1200 in the fall, has been great. I opted for parts just below the top of the line because I thought that would be the sweet spot. (I opted for a GTX 1070 rather than a 1080 for example). I have had no issues so far, but perhaps over the longer term I'll wish I had opted for the top of the line build. That is not the case yet. I see your point about buying for the long term savings rather than needing to upgrade every year. I haven't yet had issues with that but that may be true over a longer period of time.
Additionally, if you choose to buy a PC prebuilt rather than building it yourself it costs a lot more so your price range becomes more accurate than my estimates. That said if I were to give a cost estimate to someone who wanted to get a PC for VR development I'd tell them they can build a PC that can run everything for around $1200 USD and it would be completely adequate for development work for at least a year or two. As someone pointed out above that doesn't include the headsets, so the whole endeavour is still quite expensive.
If you're just getting in as a consumer, a $1000 VR-capable PC is going to age very quickly. In my experience, the only way to get any sort of legs out of a high-end purchase is to buy the top of the line. Unless you're buying right before a major product release, my experience has been that you end up spending less year over year than if you try to commoditize.
But I took the person I was replying to to be asking about getting in as a developer, considering the blog post is about getting in as a developer, and considering this site is full of developers. $2000 has been very consistently the price one pays for "top of the line PC with parts that aren't going to shit the bed". You should not cheap out on a development PC for VR. You're going to be doing a lot of experimenting and running up against performance limits during development. You should have some headroom to avoid giving yourself a headache for the day.
But go ahead. Buy a Radeon GPU. Have fun not being able to use your VR headset right before a crucial demo because of some obscure driver issue. Cheap out on a crappy power supply. See how many investors you get for our VR startup when your demo PC won't even start.