Well, Christi is the only dive op I've used in Coz and price was one of our considerations. While diving off of her boats I took notice of many dive ops. Some were diving off recreational fishing boats with zero sun cover. Some had many, many people aboard (I was never on a boat with more than 5 other people). On the day I dove the devil's throat, there were people making an emergency out-of-air ascent to the surface on our way down. Pedro (our DM from bluext) confided that the only reason he took us there is that he checked us out for it on previous dives without us knowing it.
Pedro was a pretty rocking DM. He would do a multi-level dive for 55-85 minutes with us without us really noticing the depth transitions so much. And yes, Pedro let us stay down 85 minutes. He notices your SAC rates on the first few dives and adjusts his level changes accordingly. Hopefully he is still there.
Christi was almost aways in the office during posted hours to help you find more dives if need be, take care of issues, or even recommend you somewhere to eat.
My dive partner and I try to dive 3 times a day. Christi often was able to get us third dives either in the afternoon or night on most days. And this was during the low season.
Expensive? Maybe compared to some of the speed boat ops. The difference in what you pay versus some of those ghetto ops from what is well worth the money. (which wasn't a big money differential by any means)
From what I've heard, there are plenty of great dive ops to pick over the ghetto ones. Where you plan to stay on Coz is a primary driver for which one you should pick.