I have the OGE kit and its expensive for the price. However I am an electrical dummy and wanted something pre-wired and ready to go. Also when I looked up the price of buying my own kit at the time it would have been within a $100-$200 dollars of a pre-made kit. You have to consider the cost of a nice hydraulic crimper and high quality cables along with time as well. Now that I have a little more electrical experience and understanding I probably would have tackled the job myself. More for the accomplishment of it.
You can buy the mounts themselves and wire it yourself and save a few hundred dollars. OGE, SDHQ, C4 Fab, Shrockworks, Genesis Off-Road all sell kits and mounts separately. Blue Sea, National Luna, IBS, Red Arc, C-tek, Perfect Switch Powergate are just a few companies that make isolators.