The seller put a BIN on the page for $175 for the Mantle, but he may have sold it for $750 and didn't want to pay the ebay fees on that amount.
If you want to prevent a BIN situation on an item, then place a significant bid. That tells the seller this is a good item. Here is an example.
These bookends were on ebay a few weeks ago. I emailed the seller asking if there was a price for which he would end the auction early. He asks what I had in mind and I made a very good offer. He said he would think about it. The night before it ended, the highest bid was waaaaaaay under what I was offering, so he ended it early despite 13 watchers. If there was more bidding activity, he probably would not have.
In the case of the item belowe, a friend of mine offered the seller 4 x what it eventually sold for and they rejected it thinking it would go higher, so it's a two way street on the old BIN early.

Mike H.