Gems and the cost to cut time.
While being in an active war clan, I'm always frustrated when my Hero's(specifically Queen) are going thru surgery because I would always have to sit out of war. Royals being the biggest part of an attack, they can make the difference from getting those extra % points to getting an extra star or reaching for that last bit of available loot.
So with that being said, the only time I have ever used gems is to cut the upgrading time of my royals so that they would be available to attack and also to test out their new powers. But I have noticed something peculiar. The price to gem the Royals time. For a full 7 day payout it is 1000 Gems. So you would think that with 3.5 days left it would go down to 500 but no. SS has done such a system that when you begin to upgrade anything, the timer of the gem counter is so much slower to that of the time counter. In fact with 2.5 days left my cost to gem the Queen upgrade to 28 was 445 gems! So I did some research and found a pretty handy blog on this with a gem calculator.
http://www.allworkallplay.org/blog/clash-of-clans-time-monetization-formulas-demistifyed/check it out and let me know what you think.