Some of these gun auction sites are nothing more then gun dealers selling on line. They have a price in mind and if you don't meet it, then there is no deal. Many of these people are profit oriented and that's all.
I have purchased a lot of muzzleloaders on line and have been lucky. Only one was not quite what the seller claimed. I guess his idea of a little pitting in the barrel and mine were really different. But overall if you look at the seller's history and some of the comments from people who have purchased in the past from them, you can get an idea of what kind of person/business you are dealing with.
I do try and purchase my rifles and scopes locally, but the small shops here just can not compete price wise with some of the retail outlet chains and the auction sites.