150-200$ sounds like an official manufacturer's devboard, but for the maker market you shouldn't have to shell out more than 30$. What are these boards you've been looking at?
Even tough it doesn't have OpenCL 2 capable GPU it has 10 cores - but something on the higher end seems very expensive and cheap boards are generation old chips with Mali450 GPUs or PI level HW.
It seems cheaper to get a cheap chinese phone with top level chipset and all the sensors and dissasemble it - maybe get one with a broken screen - although it's a gamble that the rest works.
Even tough it doesn't have OpenCL 2 capable GPU it has 10 cores - but something on the higher end seems very expensive and cheap boards are generation old chips with Mali450 GPUs or PI level HW.
It seems cheaper to get a cheap chinese phone with top level chipset and all the sensors and dissasemble it - maybe get one with a broken screen - although it's a gamble that the rest works.