I have spent some time with the HTC Vive, Oculus Rift, and a WMR headset, so hopefully the following summaries will help you make a good decision.
Windows Mixed Reality headset kits (the ones with controllers, not sure if there exist ones without them though I haven't seen any) run the cheapest at around $200-$400 and don't require anything extra. I'm not sure where you heard of a $500 camera being required, but that isn't the case. This headset only has one split-end cable coming out of it that is plugged your graphics card and one usb port. It is tracked "inside-out" and uses the least cable hookups of any headset, which is very convenient. I don't find as comfortable as either the HTC Vive or the Oculus Rift though. It's not terrible, just not great. Perhaps with some customizations one could make it better.
The Oculus Rift headset kit comes with two sensors which give you 180 degree, "forward-facing" tracking. If you want to be able to turn 360 degrees any way you want and walk around your room space, you will need to purchase a third sensor. Some people claim adding a fourth one (one for each corner of the room) will improve tracking. The Oculus Rift system requires you to plug in the most cables of any headset, as each sensor is plugged in via usb, along with the headset itself, which I found inconvenient. It arguably has the best controllers of any headset right now, though I personally find them to be a bit on the heavy side, especially in comparison to the controllers for WMR headsets (which are the lightest I've used). I find the comfort of the Rift to be slightly better than the WMR headsets, but lacking a nose rest (which I think you may be able to add on yourself, though I am not sure on this).
The HTC Vive uses two sensors in the opposite corners of the room which do not need to be plugged into your computer-just an ac outlet for power. The tracking technology in these is better and more accurate than the previous two systems, though the difference isn't too glaringly different. This headset runs a split-end line to a link box which requires ac power. Another split-end cable runs from the opposite end of this link box into your computer (video card/usb). Setup times for both the Oculus Rift and HTC Vive are pretty similar. The controllers for this system and the WMR headsets are very similar, though I honestly liked the WMR controllers the most simply because of how light they were (far lighter than the Rift or Vive's). I found the Vive to easily be the most comfortable headset, at least when looking at the stock configurations of each headset.
90% of games made for the HTC Vive will work fairly well with WMR headsets also, though many do not take advantage of the added joysticks on WMR headset controllers (not really a big deal). The Rift seems to generally have more issues running Steam games made for the HTC Vive, though most new Steam VR apps are releasing with good support for all three headsets at this point. The only games the HTC Vive and WMR headsets may have a little trouble running are Oculus exclusive titles on the Oculus store, though I cannot comment too much on that since I haven't tried that before.
Hopefully this information helps you make a better decision. I like the HTC Vive the best, though if I had a tighter budget or didn't want to hassle much with the setup process I would just get a WMR headset and customize/mod it however I could to make its comfort better. The WMR would also be very mobile and great paired with a laptop. For your reference, I used Dell's WMR headset.