No. You weren't scammed. After I read your post I'll explain why.
Not sure how this could ever be construed as a "scam". Scam's aren't really possible anyways. The 100g might be his OCD or he's doing this as a joke. The underselling the market might be him intentionally dropping the prices of that mini/year of minis so that he can buy them at a cheaper price in the coming weeks. Stranger things have happened.
For now... Just continue on. Worst case scenario it's a duped mini and anet might figure out you have one and will possibly remove it from your account. I wouldn't worry.
Last edited by carnage-runner; May 30, 2012 at 06:35 PM // 18:35..