A four-mana 2/2, Nightshade Harvester is likely to grow big fast, especially if you have a lot of opponents
Narset has also found her way into the Commander format, becoming one of the best cards to include in a mono-blue Commander deck
A more widespread card that features an item or less popular Pokmon might go for $1 to $10
Just be prepared to reap a lot of salt when you cast it
There was the dreadful Cluestone cycle, including Boros Cluestone from Dragons Maze, there was the Monument cycle that turned into creatures from Dragons of Tarkir, including Atarka Monument, and there were more popular cycles, like the Signets from the original Ravnica block, which included Dimir Signet
These are small enough numbers to normally avoid drawing the tables ire, but large enough to give you a solid buffer against early attacks