Yep, the bombarded the lead with protons until enough stuck that it was "gold". But, it was very radioactive.

Um, if T.H.E.Y. have that technology, they probably have the next technology that can just basically make gold out of the aether.

T.H.E.Y. are not inventive. T.H.E.Y. are only cunning. And T.H.E.Y. probably want gold because their masters, the El, loved gold. So, because T.H.E.Y. are so secretive, the technology has probably gone backwards, and not forwards.

If T.H.E.Y. were making gold, T.H.E.Y. would probably still horde it. But yeah, it could be the next fiat.