This technique goes back long before the Internet. I recall working in a computer store where it was a standard practice to give someone a quote with an expiry date, and if they missed the time limit extra money would be tacked on with some made-up BS excuse (We sold out of Foobars and the new shipment came in at a higher price).

It was the exact same reasoning: The customer walked away, shopped around, and came back because we have everyone else beat. So now we need to raise our price as much as possible without making it worth their while to go back to someone else.

And in fact, they probably are in our place because someone else raised their price on them, or disclosed hidden gotchas, so we have leverage.