He's considering Cancun to save money. How much is that plane?
If his baggage isn't huge, I get my tickets by email for about 49 pp one way. (DO NOT buy them online. Email for best quote and negotiate.) That includes a shuttle from the CUN FBO to whichever international terminal.
As compared to 12.50 for the ferry? And what like 10 for the bus? And there is a 6 am ferry at the moment, I believe. If you look at a ferry company schedule, there will be two. One for certain days and one for other days. BOTH of those schedule run every day, it just means the other ferry company has that run.