Yep, it's a time-sensitive market, as they're racing teams that will take days/weeks/months/never to catch up.
* Dark web resellers: "20-50% take for X cards at Y $ in Z time" => additional jumbling (drop shipping, ...) and exit points (discounted $ for anonymous purchases for/during illegal activities)
* Normal marketplaces: "$100 starbucks card, 10% off!"
* Sell to physical retailers like small corner stores
The approach & time will all impact % retained
Edit: Here's a fun one, esp. when you think through all the ground operations / people in the drug supply chain: https://losspreventionmedia.com/gift-cards-have-become-a-com... . We work with a lot of sec/fraud teams, where I've repeatedly heard the story "At $100M-1B revenue the finance wizards started a gift cards program, but it became such a pain point that we canceled it."