... I will never go back as what I saw was that Cayman is extremely overrated, vastly over-hyped, and totally over-priced. There are way too many much better dive destinations that are less expensive and just as easy to get to.
The Caymans are expensive, there's no doubt about that, but they are beautiful and we have come to love the amenities of GC and the wonderful diving of BC and LC.
I have been to the Caymans 5 times and have never been short-changed. The cash registers have a button for "$US" and they give you back the exact change in Caymanian money. Unfortunately the exchange rate is not in our favor. And they often add a gratuity for dining so you have to check the bill carefully to avoid excessive over-tipping.
Eating out 3 times a day is really expensive. We usually stay at a one-bedroom kitchen apartment on GC and cook some meals and then go to an all-inclusive resort on the sister islands or get on a live-aboard.
You definitely didn't have a good vendor, leader, or itinerary. There is good diving off GC although I feel that the sister islands are superior. But you should have had a much better trip as long as the weather was cooperative; perhaps you can complain and ask for a partial refund?
Have you ever tried a live-aboard? We have found that a high quality live-aboard dive boat in a great location is the most economical dive trip. The trip includes your food, lodging, and many, many dives; and they tend to visit the more pristine, less-frequented dive sites. When you figure out the cost-per-dive for a live-aboard vacation versus a land-based dive trip doing boat dives; then the live-aboard is usually a great bargain.
But you won't have all the attractions (dining, beaches, night life, activities) that are often available on a land-based trip and if you are traveling with non-divers then a live-aboard can be very boring for your companions. Bad weather can ruin any dive trip but it can be a miserable experience if you are stuck on a boat!
I am sorry that you had a bad experience on GC; I hope that your next trip is better.