Decriminalization is a cowardly half-solution that only creates more problems, leaves violent gangs in charge and does nothing to improve the purity of drugs. A measured and thoughtful legalization program for the most popular drugs is the only solution if we want to curtail black market dominance and save human lives.
Ok, when it's your friend or relative that suffers an overdose you can revisit your opinion that it's better to force people to buy impure drugs than to forge a different path forward that places a higher value on human life.
You're incredibly misinformed on this issue. The prohibition War on Drugs is what keeps drug prices up, organized criminality and violence, and the over-incarceration of mostly poor people. Take away the difficulty of access and the ridiculous criminal penalties for nonviolent infractions, and street prices drop.
In all cases I’m aware of, “decriminalization” refers to legalizing possession of small end user amounts. It doesn’t legalize production or sales, so the issues you described remain.
If low drug prices is what you want, we should legalize the production and sales of drugs, but keep usage illegal.