There are 2 levels of Subscription. The first is the standard subscription and costs $199 for the first year ($149 renewals). The second level is the Technet Professional and it costs $349 for the first year ($249 renewals). There is a third option which is the professional version with media (meaning that MS will physically send you all of the software on disk) This option is $599.
This page provides a good breakdown on what you get with each version;
Buy a TechNet subscription
Honestly, the cost of Technet is tiny for everything you get. But as other have said, these keys are not intended to be shared with others, sold, or used to support a business in any way. They are strictly for your own personal evaluation use of the software