How much is a can of billy carter beer?

Billy Carter was a real person, but there is no beer brand named after him.

You might be thinking of "Billy Beer," which was a brand of beer produced by Falstaff Brewing Corporation in the 1970s. It was marketed as a "light beer" and was associated with President Jimmy Carter's brother, Billy Carter.

Billy Beer was discontinued in the early 1980s and there is no way to buy it new today. You might find some vintage cans online, but they would be considered collector's items and likely quite expensive.