In terms of price there is, before purchase of your head-mounted display (HMD) is considered, the need to make sure you have an adequately functioning PC. Fortunately the base cost of this has begun to significantly reduce over the last 18 months on both PC and laptop thanks largely to the efforts of the hardware companies working with the the likes of Oculus in order to achieve this. Once you are sure you have an adequate level of hardware (see the Statistics section) you have can move on to the HMDs themselves.
The HTC Vive will set you back $799 (USD), which includes everything you require. The HMD itself, Lighthouse sensors, controllers and cables. However the total does not include sale related taxes such as US state sales taxes and does not include shipping costs in some countries if buying from HTC directly.
Until relatively recently the The Oculus Rift also retailed for approximately $800 (USD) although this price relates to a bundle combining an Oculus Rift HMD and an Oculus Touch kit, thus give a comparable package and to the HTC Vive. However, as of March 2017 Oculus announced a price drop bringing the bundle down in price to $598, with the Oculus Rift at $499, Oculus Touch at $99 and the purcahse of an additional sensor reduced to $59.
