Upstream has released updates that appear to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
Bukkit Changes:
9a80d38c SPIGOT-336, SPIGOT-3366, SPIGOT-5768, SPIGOT-6409, SPIGOT-6861, PR-722: Add EntityRemoveEvent
258086d9 SPIGOT-7417, PR-967: Add Sign#getTargetSide and Sign#getAllowedEditor
ffaba051 SPIGOT-7584: Add missing Tag.ITEMS_NON_FLAMMABLE_WOOD
CraftBukkit Changes:
98b6c1ac7 SPIGOT-7589 Fix NullPointerException when bans expire
a2736ddb0 SPIGOT-336, SPIGOT-3366, SPIGOT-5768, SPIGOT-6409, SPIGOT-6861, PR-1008: Add EntityRemoveEvent
5bf12cb89 SPIGOT-7565: Throw a more descriptive error message when a developer tries to spawn an entity from a CraftBukkit class
76d95fe7e SPIGOT-7417, PR-1343: Add Sign#getTargetSide and Sign#getAllowedEditor
Spigot Changes:
e9ec5485 Rebuild patches
f1b62e0c Rebuild patches
Cost is a property of individual enchantments, and is used by vanilla in combination with environmental aspects like tool enchantability and bookshelf count to determine the final cost of an enchantment as shown in an enchanting table.
Having access to the base cost of an enchantment using these vanilla methods can allow plugin developers to determine the "value" of an enchantment, and use it in custom logic where needed. I came across this recently when trying to assign an economic value to enchantments during tool repairing, and noticed these values don't seem to be obtainable under the current API.
