You've advertised 9 cars for sale since June last year.
If you read the rules when you signed up to the site [which incidentally you would have clicked "I agree to the terms and conditions"], or posted in the various for sale rooms, the suspension of your goldmembership wouldn't have come as a shock to you. If your memory needs refreshing
Click Here and pay special attention to rule 2.
The fact is, whatever you're selling is sold for more than you paid for it or more than it cost for you to make, with the intention of a profit.
I haven't looked up the dictionary definition of a Trader, but I can imagine it's just a better worded version of that.