Static Grade weapons or artifacts have the strength of Tier 2 Intermediate Rank Mage's power. They are mostly used to increase cultivation. Like the Wheel Stone obtained by Gu Jin.
Holy Grade weapons or artifacts have the strength of Tier 3 Advanced Rank Mage's power. They have both defensive and offensive power.
Spirit Grade weapons or artifacts have the strength of Tier 1 Super Mage's power. They mostly have strong defensive power.
Soul Grade weapons or artifacts have the strength of Tier 2 Emperor Rank Mage's power. They are the most useful tools considering how they can not only attack, and defend but also sometimes have the effect to rebound the attack.
Of course, each grade has its own variations too but this was the most general knowledge about the artifacts.
Soul Grade artifacts were not something that could be obtained by rich people. No! To buy a soul-grade artifact you at least need to have a high military post and wealth.