but doesn’t this suggest the higher prices are for those new to the sites?
Apparently, it depends upon various factors. According to oh8, in his experience once he found a price he liked then returned later to purchase, the price had mysteriously gone up since his last visit. Closing out the browser (which cleared out the cookies) reset the noted site to the lower price offering.
Other sites seem to offer lower prices if you log onto them versus if you are just a casual browser. It pays to keep an eye on the sites you are interested in making a purchase from and trying alternate methods to see if you can get a lower price.
The article mentions more.