OP simply failed to read the SDSB rules and is now upset about it, ranting that AA erroneously charged the fee when AA was not in error. It was OP.

It's fine not to like a policy and if one doesn't like it enough to fly another carrier. But, complaining that AA abided by the rules OP agreed to doesn't really mean much.

For $75 on flights between the 50 United States, Puerto Rico and the U.S. Virgin Islands (USVI) you may standby on an earlier flight as long as the alternate flight:

Has the same origin and destination
Is for the same calendar day of departure
Is marketed and operated by American Airlines or American Eagle
You cannot change your itinerary to a city with multiple airports or to a different connecting city.

Same-day standby charges are automatically refunded if you're not accommodated on the flight you standby for.

AAdvantageŽ elite members may standby for earlier or later flights.