Check out Honduras. Prices seem to be reasonable from my research. I've been looking at Anthony's Key Resort, their all inclusive package including 3 single tank boat dives a day, 2 night dives during the 7 day package, 3 meals a day is no more than $1650 per person. That's just an example.
Other resorts I'm looking at are Deep Blue Utila ($1000 per person, all inclusive), Barefoot Divers Roatan, Reef House Resort. There are several others, but roughly $900-$1600 per person all inclusive seems to be able to get you a pretty nice dive vacation. Flights seem to be about $900/pp.