If memory serves me correctly, I believe Steve Frizza was charging around $200 a roll to develop Kodachrome and got scoffed at on this forum, so he retracted the offer for his service. Mind you, he was probably the only person in the world offering the service, so not a bad deal...
You have to have a timed red light in the right color spectrum for the red sensitive layer in which you then develop the cyan layer after and the. A blue light in the right color spectrum for the blue sensitive layer and then you develop yellow layer after. If you’ve exposed both red and blue layers to completion without contaminating the green layer (for magenta) and have developed cyan and yellow at the right amount of development time you then exposure the last layer, green sensitive to tons of full spectrum light and develop the magenta layer.