My break even costs have never been calculated and I don't really care about those...
I could not do the dives I wanted to do on OC anymore. 2x 200ft dives per day for a week in Lake Huron? No wasn't happening without a CCR. The nearest dive shop with trimix is in Detroit, 3 hrs away. The charter could "sort of" support an OC diver - like one. But a 6-pack full of them? No wasn't happening, she can fill the boat with CCR divers who pay just as much and use less fuel (a CCR plus 2 BO al80s is a lot less weight than 2 sets of doubles and deco bottles per diver) and doesn't even want to bother with OC trimix divers.
Cave diving a week in Northern Vancouver Island? Nearest compressor is 2+ hours away at a fire station, they have air, and a yoke valve adapter... Trimix? No wasn't happening. Bringing my own compressor, helium, and OC tanks? Yes I did it a few years. Yes I had to replace the springs in my truck for over $500. The wear and tear on my truck and me from hauling OC tanks through the bush for what I'd call short (2hr) cave dives was brutal.
I might have broken even at about 200 CCR hours in 4 years, but that wasn't my purpose from the outset.