It's because users of opiates can build up a really high tolerance. Like an order of magnitude more than would knock a non-user off his rocker will be barely e

It's because users of opiates can build up a really high tolerance. Like an order of magnitude more than would knock a non-user off his rocker will be barely enough to feel anything. And heroin is really expensive. So imagine someone who is extremely frugal buying expired food. Only cranked up to 10.