https://theintercept.com/2018/11/23/bitcoin-gift-card-trading-scams/
This is a good article, but it's a much better article if you understand that everyone here is facilitating an underlying theft. The Bitcoin / gift card ecosystem isn't an arbitrage opportunity or payments facilitation; it is a laundry.
Part of the genius of the operation is it gives cashers like Eric here some plausible deniability and, from an ecosystemic level, allows the ecosystem to user cashers who "don't look like criminals" & are extraordinarily unlikely to attract sustained negative official attention.
One of my best comments on HN, which I'm going to avoid linking to to avoid causing a one-time mistake to follow relatively benign-intent startup founder around for life, was "Do you understand who is willing to receive $50 in consideration for $100 in Starbucks cards at scale?"