By the same logic, the price of food should correlate to the number of crimes committed to obtain it. But far more is spent on food than drugs, and most theft is to buy drugs, so something is different.
The difference is that normal people work at jobs to obtain money for food, but serious drug addicts are incapable of working a regular job and so have to steal to support their drug habit (and for their food as well).
So in fact, crime is proportional to how much drugs interfere with ability to hold a job.
There's a huge segment of "serious drug addicts" in our population that show exactly what crack and meth users would be like if their drugs of choice were legalized: it's called Alcoholics Anonymous. Are you equally concerned about being robbed and beaten by an alcoholic? Their drug of choice has been legal for quite some time.
The difference is that normal people work at jobs to obtain money for food, but serious drug addicts are incapable of working a regular job and so have to steal to support their drug habit (and for their food as well).
So in fact, crime is proportional to how much drugs interfere with ability to hold a job.