I'm a Red Carpet member. I haven't heard that one can pay a daily fee to get in, but maybe someone else can give you an answer. I hope that's not the case. In some airports, the Clubs are crowded enough during peak hours.
A relaxed setting with plenty of phones, computer hook ups, newspapers, television, complimentary beverages (non alcohlic in the USA) and snacks is what you'll get. Alcohol is available at much cheaper prices than you'll pay in the public areas of airports. You can check in for your flight if you have no luggage to check, which is a great service. Usually minimal, if any, lines. The staff in the Red Carpet rooms are usually the best United has.
Showers are available to first and business class passengers in the "Arrivals by United" program at certain international airports. I believe they describe it in the www.ual.com website. I've never taken advantage of it, but it looks attractive.
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