JUTA bus from the airport to Negril I think was $30USD one way, but the problem with that is you'll have to wait at the airport until the bus fills up and it's point A to point B. While you're waiting, sitting at Margaritaville on the bus side of the departure door won't work, not at 8$USD for a Red Stripe. I think you can still get a car to take you to Negril for $50-$60, with Red Stripe stops on the way. Lot's of drivers waiting at the door for walkout customers. $80 for a van. Also the Knutsford runs from MBJ to Negril but only one bus per day so the timing might not work out. Here is the JUTA bus link.

https://www.jutatoursja.com/