science

And my point is that, given how deep these things seems to be, it is cheaper to haul them on the surface than sending a diver down, even if you need to do some unscheduled maintenance, especially because sending down a commercial diver (the only that can hope to work this deep) is not an easy feat in itself.

Obviously it will be expensive either way, I was only pointing out that sending down commercial divers a lot of additional levels of complexity (decompression periods measured in days or weeks, need to hire many more highly specialized people and from a way smaller pool and so on) that will drive up the price.