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.
