"I'm not really talking about what makes more, but just the overhead involved which one costs more to operate."
I can answer this question.......
The propped coral will always cost more to operate, it will never be cheaper then a coral that gets shipped from the wholesaler and sold. The propped coral will use resources that the wild colony will never use. The reason it cost more is that it stays around longer, as long as it is healthy. It will pay the initial cost( the money to acquire the wild colony) off as soon as a few frags are sold. After that it will be overhead that it will then have to pay off, such as salt for water changes, electricity, rent for facility or home whatever, don't forget your time as that has a cost in it as well.
The longer something sits in your tank and does not generate any income the more it cost you. Just like those drab zoanthids that nobody buys, they actually cost a person more in the long run as they use up resources. But in these cases they have to be discounted as the space they take up cost you as well, cause they are taking up space that can be used for either A. A faster selling coral or B. A better morph for propagation that will lead to more income from a higher demand for the polyps.
To actually do nothing but propagation is very costly as it is much more resource intensive then some thing that is bought and sold within a weeks time. The coral you sell within that week cost you little as far as overhead, but the price of it will include a certain amount of overhead. This is why when the first captive bred fish were hitting the
market they cost so much more. Plus there wasn't as big a demand for them. The cost was actually prohibitive towards sales because at that time the hobbyist were not a conscientious about captive breeding. Why pay more then 2x the amount for the same fish I can pay less for. But once they realized that the life expectancy of captive raised fish was A. longer, B. More adapted to captive life, C. The death rate was dramatically less they started to take off. As well as the hobbyist began to realize the importance of captive propagation to the hobby and the reefs it became more viable. The same thing is now happening with more and more corals. This will in the end drive down the price as I can sell more captive raised fish and corals and the volume of sales can under cut the price that was once asked per captive coral or fish because it can now be spread out to ore specimens then just the few that were being sold in the beginning......
The trend in the beginning really killed a bunch of captive farms because the hobbyist were not ready for it yet. But times have changed and I think the profitability of captive raised coral and fish have yet to be seen. In the near future it will be a very viable option instead of actually ordering wild colonies and fish. I think also eventually the only reason for wild caught will be to gain new specimens for propagation.