Question : What day in the next four weeks has the best fares?
Answer : Since low prices are preferred, look at Mar 9th. As of Feb 20th, it's showing the cheapest ticket sales at $303. That is 19% below the average price for this route, so you can spend that extra money on a fun experience in Charleston.
Question : How much should a trip from Key West (EYW) to Charleston (CHS) cost?
Answer : Ranging from $303 to $423, prices for EYW to CHS change much less than most routes in the United States. Prices tend to be lower the further out you book.
Question : How long do most people visit Charleston?
Answer : Of course you're not most people, but if you were, you'd stay roughly four days.
Question : Is price more important than specific travel days for you?
Answer : The cheapest day to fly in March is Thursday. Having flexibility in your travel plans means you can save more, so be sure to plan ahead when possible.