I'm curious how you determined that you saved money with the skylights? Especially that much money. During daylight hours, how many lights do you turn on in a room with a skylight compared to not having a skylight? Most people are not even home when it's daylight out, but for those that are, do you normally keep your lights on?
Since a skylight offers a very low, or even no R value, how much energy are you losing through your skylight heating and cooling your home? Here in Texas, AC is the biggest expense of any home owner. Heat transfers through skylights a lot worse then a side window because of the up down properties of heat and cold air. If you have anywhere from R30 to R60 in your attic, what is it where the skylight goes through your ceiling and roof without any of that R value?
From what I understand, nobody even notices an extra light on all the time, but when you remove a skylight and insulate that area of your attic, you notice it right away when you get your energy bill!!!! And that was when we all had incandescent light bulbs. With LED bulbs, it make even less financial sense to have a skylight.