$4K throwing off $20/mo assumes roughly 6% net APY, which is right around today's large-TVL stablecoin band: DefiLlama has Aave v3 USDC on Ethereum at ~7.2% and Fluid USDC at ~7.0%, while Spark-style savings rates sit closer to 3-4%. The catch is wording: $20 covers ChatGPT Plus, not the $200 Pro tier, and the user is swapping a SaaS bill for smart-contract, oracle, governance, and rate-reset risk. As a funnel, though, this is probably how DeFi goes mainstream: hide APY-maxxing behind a concrete liability instead of asking normal users to care about stablecoin basis.

Top comment by @Benthic