Actually, its like this.
SCC gives bonus invites 1-2 times a year to all of its members, ranging from 1-4 invites, these invites should never be sold.
Other way by which I and some of my friends got the invites are by donating to SCC, this is actually not called trading or selling because the person who wants the invite donates from your account and you in return get the invite, this way is totally legal and is being practiced on many other trackers.
And btw he did gave it for free to @qaiser.