Getting plenty of play will probably have boosted its market value at least a little, but ultimately it's the low supply, inherent to any prize card, that has made Diablosis so expensive
Scaling Your TCG Business: The Path Forward In 2026, the barrier to entry for TCGs is no longer access to manufacturingit is supply chain reliability and scalability
It's literally an Unclaimed Territory 99.99% of the time as spending 6(!) total mana to make a 1/1 Sliver token is such an awful rate that it might as well not even be on the card -- if you regularly activate it then I'd recommend rebuilding the deck, maybe add some more card draw so you have better things to spend your mana on
Mono U could likely support a rare mill deck (Ruin Crab, Maddening Cacophony, Field Research, Glacial Grasp, blockers like Skyclave Squid to fill the curve, etc), though most Mono-Blue inclined decks will likely just end up UB
Enter Blech, Loafing Pest, a 3/4 legendary Pest creature that costs one generic, one green, and one black mana