The standard morning dive outing in Kona tends to be a two tank outing, diving one tank at each of two locations. Some operators do offer a three tank day on occasion. I'm not aware of any at this point that offer a regularly scheduled 3 tank trip, but several will do it when there are enough customers to make a go of it.
We did a three tanker yesterday. Our first dive was up north above the airport at a spot a handful of us go to on occasional basis. It's a great live boat dive with both deep and shallow reefs so we can do a deeper multilevel dive and still do a long dive. Highlights of that dive were a manta ray right off the bat, and the reef structure of the dive... lots of grand topography.
Our second dive was at Pipe Dream, which is right off the westernmost point of the island on a large dropoff. There are a number of large pipes in the water. The one pictured above is basically a 6-8 foot diameter culvert that begins at about 60' of depth and goes down to about 120'. I'm not exactly sure what the plan was for this particular pipe or if it was ever used, there are several deep water pipes in use there for collecting deep seawater for various uses at the Natural Energy Lab.
Our third dive was at the Lone Tree and Suck 'em up diving area, which features swim through lava tubes as well as reef.
In addition to the ray, highlights of the day were reef sharks, a young yellow frogfish, lots of eels, a turtle, a blue dragon nudibranch, Saddleback butterflyfish, lots of other interesting fish and critters, and lots of great reef structure.
We only run three tank dives when we get enough divers to make it a go. I have a policy on these trips that some people don't like, and others appreciate --- I'm not going to do them with divers I don't know --- The dives we do on these may be a slight bit more advanced, requiring a live boat (which means no down lines, and people who have ear problems or need a line for descents or safety stops probably shouldn't be trying it 'til they've worked through it) or have dropoffs that are deep enough that divers who don't pay attention can get themselves into trouble. It usually only takes a day of diving to tell if a diver's ready for this type of trip. --- Here's the reason I do this... I've been a paying customer on more "advanced" outings with other operators over the years, and on some occasions there have been a diver or divers who obviously were still working out bugs in either their skills or awareness, it inconvenienced both the crew and the other paying customers. This shouldn't be the case when you are billing an outing as a bit more advanced, as these dives really aren't all that advanced to the point that a day or two of diving (with the crew you are using, so you know how they run things) beforehand can't remedy most of the problems I've seen.
Prices for the three tankers run all over the board from what I've seen. I currently (I may be changing prices later this spring, hopefully not much of a bump if it occurs) charge $159 per person and up depending on how far we go (extra fuel, extra time, etc). Where we go will depend on the conditions, both water and weather, of the day - I'm not going to intentionally run an hour to hour and a half from port when the weather's supposed to be iffy. You tend to see a lot more of the 3 tank trips come together in the late summer and early fall when the water and weather conditions are generally consistant and nice. Yesterday we had some very good divers on board and the dives lasted about an average of 75-80 minutes or so... it was a nice long day of diving.