Yes. Your $50 reward is paid once all 3 friends in a group have qualified. It isn't paid per friend, and you don't get part of it for 1 or 2.
A friend qualifies when they reach $200 in completed card payments within 60 days of entering your code. Spend after the 60 days doesn't count, so a friend who doesn't reach $200 in time won't count toward your reward.
Friends are grouped in the order they qualify. Your 4th, 5th and 6th qualified friends make up your next group, and so on.
You can see each friend's progress in the app.