Res sacrae is even more extreme than grinding your ark to stage 10. To equip lvl 2 res sacrae gems, you already have to spend about 700 blessed gems + a few hundred million silvers iirc.
Now imagine, the res sacrae has 20 levels, and at certain stages the requirement takes a steep increase in material costs. That goes far beyond the costs of Arch Stones and Karaliene set (though Lucifieri crafting ist just insane, especially if you cannot beat Tell Harsha at higher difficulties because you lack the equipment).
The goddess and demon sets have okish costs with 1 Arch stone fragment per part (so 4 per set), but since they can be leveled,too,just like vaivoras, with multiples, it’s better to say that you need about 16 Arch stone fragments (so 1.6 Arch stones) to complete a single set of 4 pieces.
If I was the developer, I would’ve put Arch stone fragments somewhere as guaranteed rewards (for example as the 500 million total damage reward for WBR) if you need to get several fragments per week to be able to craft all the equipment before it becomes outdated.