My guess is that the seller had the item listed on more than one web site and it sold on one of the other web sites. After it sold the seller probably forgot to remove the listing (or didn't get time to) and was reminded of that once you tried to purchase the already sold item. I sheepishly admit that I've been guilty of that once or twice over the years and I really felt bad about it and was very apologetic. As far as Half.com knew, I still had the item available for sale. I'm guessing the same thing happened here.
Yep. That happens more than it should. That and sellers just listing tons of stuff from wholesalers that they may or may not actually have or be able to get.
As for the "bait and switch", I really think it's just sloppy coding and the system doesn't catch up when things have sold. Again, it shouldn't be happening as often as it does, but I don't think there's anything nefarious going on.
This kind of c**p has been going on for years. I complained to half.com about the problem of lowest price mispricing years ago. If it is a software problem they have had more than enough time to remedy the issue. My guess it is for the reasons previously mentioned herein.
I had a similar issue with ..........someone....... several years back. I sent the company a "bill" for my damages, ie the cost of cover. I explained that it would cost me $15 dollars more to buy the same item from someone else that I had just purchased from them. Therefore, please forward the money to me so that I would have the benefit of my bargain that it had just failed to live up to. All of these on line sellers always include that stuff about "Be sure you want this item because once you click you are CONTRACTURALLY bound. Well if that is the case, lets have some contract damages for the buyers....Of course, the problem is the cost of collection (among others), but the principal is certainly there. I cannot believe the online sites tolerate this behavior.