ScubaBrucie

It is interesting to work out the cost per dive after adding in all relevant expenditure.
For instance Red Sea liveaboards are much cheaper per dive than staying in a hotel and day diving, you do twice as many dives and the food is full board.
Likewise for me UK weekend sea diving is more expensive per dive than Red Sea diving. This is because I live in the middle of Britain so have to pay for travel and accomodation.
Bonaire is really cheap as long as your stay is not too short and you can amortise the airfare over more dives. The reason it is cheap is because you are shore diving, hence no boat to pay for and because the diving is unlimited, you just pay per day. We did 5 dives one day but you could easily do 7. So if you did 100 dives over just over a fortnight a £400 airfare costs £4 per dive.
Going to Puero Galera in the Phillippines is also cheap. Once again the airfare is the main factor so you need a long stay to average it across more dives. Guided boat dives are US$22 but I get a 15% repeat customer discount. A room can be had for US$100 a week with air conditioning, US$50 without. Everything else is third world prices.
Spain is really expensive with boat dives costing between 30 and 40 euros. Only 2 dives a day where I go and high European cost of living. The airfare is a lot less but the other costs soon catch up.

It is common on Red Sea liveaboards to do 4 and sometimes 5 dives a day.
As long as you dive triangular profiles and have a minimum one hour surface interval this works for many thousands of people.
In Bonaire we were only doing shore dives so the profiles were very triangular with a lot of time above 10 metres. Each dive was to 20 ish metres, little point in going deeper on the reef. Dive time was between 40 and 50 minutes because in a 3mm we were getting cold by then, we finished with lots of nitrox. Once again minimum surface interval was an hour. Doing this our computers never got anywhere near our ND limits.
People do dive 6 and even 7 times a day on Bonaire. It costs the same no matter how many you do. This is how to do it. First dive involves getting up whilst it is still dark and doing a pre breakfast dive, just drop onto the house reef. Then 2 dives in the morning and 2 in the afternoon a dusk dive at say half past 6 and then a true night dive just after 8.
Bonaire reefs are rated the best in the Western Atlantic so these dives are very worthwhile, there is always plenty to see and the sites are often very different from each other. Recent sightings include a Hammerhead and a Whaleshark. Doing the fish ID course added extra value to every