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The IMRXT1011 is $1.70 when bought in bulk from China from various vendors - it can do most of the things the Teensy has.

A reputable vendor: https://www.lcsc.com/product-detail/Microcontrollers-MCU-MPU...

The IMXRT1064 can be had at $7: https://www.lcsc.com/product-detail/Microcontrollers-MCU-MPU...