Due to the differences in the cutting process, the backs of JP prints almost always have a thin white border around the black border
Kaladesh had compounding factors, namely that energy was a complicated new mechanic with several costs having been misjudged, but had the designers been able to easily slap colored mana costs on most of the artifacts without tradition turning them away, things could have been different
Your opponent plays a big creature, you counter it
Over the last five years, Cryptolith Rite has increased significantly in value, being propelled by EDH play and lack of reprints
Mufasa - Ruler of the King's Rock (V.2) Mufasa is the crown jewel of the "Skylight" set
Lifegain is also technically a payoff but mostly it is an incidental one, it isn't a route to victory and shouldn't be the focus of a plan