I'd guess that they are caching this information to reduce the strain on the server. Maybe they've significantly increased the duration of a cached page, which like you said, makes no sense for a deal site where the timer, the amount sold, and the amount left is crucial and needs to be available real-time. In terms of budget, it was probably cheaper just to cache the pages longer than to provide more resources to the servers.
The one thing you can try, is to try this on another computer with a different internet connection and browser. If the same thing happens there, there's nothing you can do about it, but if this fixes the issue, then you've narrowed down the issue to your computer, browser, or internet connection.