That formula is so inaccurate and undercutting of the actual price, and I don't care if some guy on TGR made it up, he isn't correct. You are taking 50% off a ski because it has been used five times? How does using a ski five times take away half the quality, camber, edge, base or topsheet? Then subtracting because of a mount? If anything, it should add to it if the buyer's BSL is within 15 mm because that just saved him $40 on a mount job. Then, you added 10% of the already discounted price when you should be adding 10% of the ORIGINAL. And the s914 is still a great binding.
I agree that he will not get his asking price, but trying to malign his sale doesn't help you either. Just think of common sense: you are stating that a pair of next year's $600 skis with good bindings hardly used is only $400? That is laughable. Those would easily go for $550-$600 on Ebay next year, so don't use a fallable formula that a random person made up because you want to feel important in his thread.
Anyway, to the author of this thread: great sticks, but this is a rough place to sell in the summer, even in the winter. Try Ebay, if you can't get what you want hold onto to them for three months and pop them on. I think asking for $550 or $600 could be reasonable to ask right now(seeing that it is summer). Best of luck.