Mega Latios ex is but one of this incredible sets highlights
This is mainly due to the need to distinguish cards from other sets
For me, the tipping point is in the card type creatures are just much better than sorceries, adding the utility of attacking and blocking, paying sacrifice and convoke costs and everything else you need a body for in Magic
Collectors often prefer to buy sealed cases or join case breaks to maximize odds of pulling one, since the chance from a single loose box is very slim
Print & age Older, smaller-print sets (first edition Base, Neo, E-Card) command a premium that modern prints can't match
Exact errors that have produced value vary, but include cards that were printed crooked, those that are missing a front or back, and cards with interesting spelling errors