You won't find that one in a LTR Collector Booster, but there's still other serialized treasures to find: The Elven, Dwarven, and Human rings of power each appeared as serialized foil Sol Ring cards (300 Elven, 700 Dwarven, 900 Human) and, as it's usually the case, extended-art and alternate scene cards are exclusive to LTR Collector Boosters
Ns Zoroark & Reshiram N from Pokemon Black and White and Black 2 and White 2 is the only trainer confirmed so far to be getting more than one Trainers Pokemon card with both his Zoroark and Reshiram being revealed in the trailer
Despite this, before October the cards price never drifted far from a range between $100 and $140
You wont always be able to trigger that effortlessly, but it will happen often enough for the Deathpriest to be a very real problem for your opponent, and the great thing is, after you make that first one, youre going to be getting value even if they do find removal for it