Hey glockit4, great question, here is a list of boat dive prices I compiled last year.
A quick search on the net reveals dive prices are creeping up, but $100 a day on Saba is high. Here are some sample rates for two tank boat dives:
Gunters, Utila, Honduras $50
Pura Vida, Roatan, Honduras $60
Koh Tao, Thailand, $66
Dive Paradise, Cozumel, $69
DiveDiveDive, Nassau Bahamas, $80
Amoray, Key Largo, Florida, $80
Octopus, St. Martin $85
Multiple dives bring the price down, 10 dive at Gunters Utila will run $200
Shore diving is way less expensive and the unlimited shore diving deals on Bonaire and Curacao can't be beat.
For Boat dives Utila or Cozumel are good values. Utila has very cheap lodging deals, and Coz is good for package deals
Caymans have great diving but will be costly topside.