Although the table claims the discount caps at 30%, it goes much higher. When the total enchantment power of blocks around the table is 100, enchant costs are 0. Above that, all enchant costs go negative. This is a situation that will almost never come up, but some mods add blocks with higher enchanting power values, so using things like the Draconium block (enchanting power of 12) from Draconic evolution will make it very easy to get total power up over 100.
I doubt this could be a cause as it is not listed as one of the things it changes, but I am using your attribute fix mod, as well. Since that uncaps other things, I figured it was worth mentioning just in case.
Tested in Minecraft version 1.12.2, Enchanting Plus version 5.0.176
Although the table claims the discount caps at 30%, it goes much higher. When the total enchantment power of blocks around the table is 100, enchant costs are 0. Above that, all enchant costs go negative. This is a situation that will almost never come up, but some mods add blocks with higher enchanting power values, so using things like the Draconium block (enchanting power of 12) from Draconic evolution will make it very easy to get total power up over 100.
I doubt this could be a cause as it is not listed as one of the things it changes, but I am using your attribute fix mod, as well. Since that uncaps other things, I figured it was worth mentioning just in case.
Tested in Minecraft version 1.12.2, Enchanting Plus version 5.0.176