The possibility that any card in Historic can be retroactively rebalanced, nerfed, or fundamentally changed at any time throws Historic deck-building into volatility, and opens the otherwise static format to unanticipated changes
Based on the latest market prices tracked on TCG Stacked, Priest of Iroas is worth about $0.04 USD for a regular copy and $0.17 USD for a foil copy
Aurelia decks tend to go in two main directions, either a very heavy equipment-focused design or in an extra combat steps style of deck
So unless something impacts it greatly (like one of the Three Rs) it will not drop in price
The Power Nine were only printed for the very first core card sets, and the group includes the Black Lotus, Ancestral Recall, Time Walk, Timetwister, and the Mox jewel cards: Mox Pearl, Mox Ruby, Mox Emerald, and Mox Jet, as well as the Mox Sapphire