Teensy is faster than the Maple mini. Clock speed is higher and it has FPU, (but its $25 not $5 !)
I just bought this board from AliExpress for under $10https://www.aliexpress.com/item/STM32F4 ... 0.0.xnyky1
But at the moment its not easy to upload to, as we don't have a working bootloader for it, and the internal USB DFU bootloader is not compatible with our existing DFU uploader
But when its working, It should be much faster than a Teensy, as clock speed is 168Mhz and it has FPU.
You can overclock the Maple Mini, but the USB doesnt work above 72Mhz.