It's hard to suggest they're not a drain on the taxpayers when the rate of welfare dependency is at 28%. Before the liberalization of Switzerland's drug laws, the rate was at 17% (Britain is 18%, Australia is 17%, US is 14%).
Regardless, even if what you say is true, and Switzerland has an abundance of productive heroin addicts in the workforce, it doesn't change the fact that they have no idea whether or not decriminalization has actually led to diminished heroin use. And that was the main finding of this study.
Your bias is showing
I wasn't trying to conceal it. Then again, I'm not getting paid to conduct surveys on social issues.