Similiar story to yours. After spending almost an hour going thru books or bins at one dealers table I had a large stack of chips to buy. I don't remember the details but I made what I thought was a very reasonable offer (somewhere around $100-$150) and instead of negotiating the dealer took all of the chips and threw them into a box and basically said "get lost". I was in absolute shock at being treated that way and more than anything mad at myself at wasting a lot of time at his table early into the convention.