Liquid cooling is one of the more expensive setups for cooling in a PC computer. Why? Well, with fans set up and ready to go, you only really need that amount of power to run them. However, with liquid cooling you would have to have power to run the fluids all around your hardware and make sure it stays cool instead of boiling as it transfers heat away from your parts.
So while I do not have an exact number on how much liquid cooling will cost you in the long run, I know that it can get expensive and should only be an option for those that really will pay the premium.
As mentioned in one of my previous posts, I save on liquid cooling (meaning I turned it off) because of the winter season. In the US, where I am from, it gets quite cold and the air is very thin. This helps the computer since I have many vents that allow cold air to go in. This means that liquid cooling does not have to be on all the time (I actually have yet to turn it on), and my temperatures are monitored and say that they are doing well.