The base cost for disenchanting a rune is 5 diamonds. The cost increases by 5 diamonds for:
- Each rune you have
- Each level in the rune you want to disenchant
The very first rune you discover has a disenchantment cost of 15 diamonds. Level up that rune once, and the cost will become 20 diamonds. After that, discover a new rune, and the cost for your first rune will become 25 diamonds.
Rune X = the rune you want to disenchant
Rune X Disenchantment Cost = 5 + [5 * Total Number of Runes] + [5 * Total Number of Rune X Levels]