Tweak enchanter cost calculation to properly implement high-max-level…

… discount

src/main/java/de/dafuqs/spectrum/blocks/enchanter/EnchanterBlockEntity.java

@@ -421,7 +421,7 @@ public static int getRequiredExperienceForEnchantment(int enchantability, Enchan
 				default -> rarityCost = 80;
 			}
 
-			float levelCost = level + ((float) level / enchantment.getMaxLevel()); // the higher the level, the pricier. But not as bad for enchantments with high max levels
+			float levelCost = level * ((float) level / enchantment.getMaxLevel()); // the higher the level, the pricier. But not as bad for enchantments with high max levels
 			float specialMulti = enchantment.isTreasure() ? 2.0F : enchantment.isCursed() ? 1.5F : 1.0F;
 			float selectionAvailabilityMod = 1.0F;
 			if (!(enchantment instanceof SpectrumEnchantment)) {