The subscription service is new. When subscribing to Viveport, you’re allowed to pick five games and apps per month, and then keep any of them the next month or swap them out for new ones. After the free one-month trial ends, the cost is $7 (£7) per month.
You can purchase a Vive headset at a discount today directly from HTC or through any of several retail partners, such as Amazon and Newegg. Out of those three, HTC is the least expensive by a buck.