https://wccftech.com/apple-offering-200-m1-mac-credit-to-return-dtk-mac-mini/

During the first half of 2020, Apple announced its transition from Intel processors to custom ARM-based chips in current Mac models we now know as the M1 Mac mini, M1 MacBook Pro, and M1 MacBook Air. To help developers get started with transitioning apps to the newer platform, an A12Z Bionic-powered Mac mini was offered for $500 and was a DTK (Developer Transition Kit). Apple is now requesting developers to send back the hardware, and they will receive some compensation for their troubles.

According to an email sent to developers that was spotted by 9to5Mac, Apple states that developers will have to return the DTK Mac mini that they paid $500 for. A new email will be sent out eventually, with instructions on how to send back the Developer Transition Kit.