That's high. Try any of the providers on the negril.com Transport page. You should be able to get a private transfer for ~$120 r/t.
We used a shared bus our very first trip, and won't do it again. Although it is economical, we waited a long time for the bus to leave the airport, the driver didn't make any stops (not even for jerk chicken and Red Stripes) and we had to wait for the bus to stop at all the AIs before we got dropped off on the West End. To me, a private driver is worth the extra money. Plus, you also get to establish a relationship with a trusted driver who you can then call for all your transportation needs during the trip