Just to give you an idea, a single high-level grade-2 array could cost over 30,000 medium-grade crystals, an excessive amount for the most prominent families in the north of the Central Continent.
The main problem was the fact that to buy and activate an array of this degree, only medium-grade crystals would be involved!
The array masters who could develop items like this were all high-level Spiritual Kings, who didn't bother with low-grade crystals, which were no longer so helpful to them.
On the other hand, the consumption of these arrays required a large amount of medium-grade crystals for these items to work perfectly.
However, the reserves of medium-grade crystals in this region were not large enough, and most of the income of the noble and wealthy families was in low-grade crystals!
