Auran coinage debased?

Treasures in ACKS encounters often seem overvalued to me. E.g., “Every slaver carries a small silver ingot stamped with a striking scorpion (150 gp value each).” Lairs and Encounters, pg. 84. Or all the bone fetishes and things in Stone of Sakkara that go for like 50 gp each.

But I believe Roman coinage in the late empire was often debased so that the actual precious metal content was only 10%. If “gold pieces” in the Auran Empire are only notionally gold pieces, but are actually 90% base metal, that could go far to explaining some of these treasure values.

Is that right (or could it be, for people like me who are a little troubled by these values)?