Neither, that was the going price. That's how much it cost with a 2 year contract. $499 is the cost of the 128GB model. Obviously they're both now dropped by $100 since the 6s/6s Plus is now available.
You didn't mention that. You said you did a 2 year contract a year ago. A normal 2 year contract will garner that price. Anyways, then you got lucky, they somehow moved your eligibility date up. Can't say without knowing the full details.