First off if you purchased this item from a liquidator or an authorized wholesaler you have the right to resell the item on ebay or any other way. When you buy items of this nature you have resell rights without any needed permissions or proof.
One question. Is there another seller selling the same item. If this item is a niche item that has only 1 seller selling it. Then it may be they are trying to put you down before you get to big and take away thier sales.
I did this not too long ago with slendertone products. I was selling replacement pads I bought direct from the manufacturer of thepads.I was the only seller that offered them. I started because I sold extra pads I had laying around and found out they were a hit on ebay. I was selling them 1 by 1 selling 2 per day for around $57.00 per package. It only cost me $4.99 to aquire them. I think it was a salehoo member that knew my username that caught on to my niche. They flooded ebay with the items and dropped thier prices so low they werent even worth listing. I should have reported that member to ebay and had them shut down. Because I knew they werent buying them from the manufacturer. If I had done this I probably would still be selling that item.