If the car is of an age old enough to be scrapped or donated, to buy an ECU or other Electronics for a similar car of a similar age probably means the replaceme

If the car is of an age old enough to be scrapped or donated, to buy an ECU or other Electronics for a similar car of a similar age probably means the replacement bits are worth more than the car is, which would make the whole exercise uneconomical, further increasing the number of scrap cars and thus, number of replacement ECUs, thereby increasing supply and reducing price.