Two major factors are behind this phenomenon: a generation of adults who grew up with Pokmon and now have the purchasing power to continue investing in the hobby, and hoarders who disrupt the distribution chain by buying large quantities of packs, boxes, and boosters with the intention of reselling them on the secondary market or finding high-value cards
This equipment is a great way to shut down aggro decks: Umezawa's Jitte gains you life, gets rid of small creatures, and overall makes combat a nightmare for your opponents
That storytelling element gives error cards a dimension that standard cards simply do not have, and in a hobby where the emotional connection to a card often matters as much as its technical specifications, a great story can add real dollar value
9 Yawgmoth's Will Banned in Legacy, Restricted in Vintage, Legal in Commander Blue is probably the worst offender when it comes to overpowered Magic cards, but black also has its fair share