Just a quick comment to let everyone know that this "glitch" is still going on with Delta.
I got the "high demand" message just after entering my credit card details, and was offered a fare that was 20% higher than what I'd been booking up to that point. First time around, I believed the message. I know that airfares can change quickly, and I figured I was just unlucky. I was almost tempted just to eat the extra cost because I didn't want to go back to the beginning and have to re-enter all my family's details, choose seats again, etc.
But I like to save money. So I went back to the beginning and chose a different flight that had the same fare as my first choice. Oh good, I thought, I'll be able to get this low airfare after all. But guess what happened. Yes, this flight was also in "high demand" with a 20% premium. At this point I felt like I was getting scammed.
Normally, I'd start looking for a different airline, but I'm using some big Delta vouchers. My wife called them and spent about 45 minutes having them manually re-enter all the details. Whaddaya know? The fare we paid over the phone ended up being the same amount as what was advertised at the beginning of the process. That's how it should be.
There is little doubt in my mind that this is intentional and that they easily make a few extra tens of thousands every day from chumps. Call it "bait and switch" or "false advertising" or whatever. But the moral of the story is that if you have to fly Delta, make your arrangements the old fashioned way, and keep one eye on your wallet.