If the member is flying, all other people on the same ticket get the lower price for the fare and the baggage.

The credit card offers some advantages(much better than paid $9 membership alone):

Potential Free or Included $9 Fare Club membership

The ability to book flights for as low as 2,500 miles o/w during off-peak periods (generally short periods in January, February, May, October, November, and December when essentially all schoolchildren nationally are in school)

Bonus miles for joining

The following benefits seem to vary by airport and how busy they are:

"Jump the line"

At check-in, valid last time in Tampa, but not being honored in Detroit where there was a huge peak crowd (and they had the sign still)

In Tampa, at security, you could jump that line like you were a first class passenger on another airline. This has never been offered in Detroit to my knowledge.

Boarding, offered on some flights. If offered now, it is often after the people with paid carryons.