As of February 25, 2017 nearly 50% of the prisoners in the Federal Prison system were doing time for drug offenses. 81,813 prisoner.
The percentage is likely quite a bit higher than that, because many drug addicts end up in prison on different charges altogether, burglary, larceny, and property offenses, for instance.
While it does not appear that the Bureau of Prisons has released its costs for the 2016 Fiscal Year at this time, in 2015 it cost an average of $31,997 per year to keep someone in the prison system (total daily cost and support cost).
For the people housed in Federal Prisons due to drug charges, that was $3 billion spent in 2015 alone. That’s just the tip of the iceberg: the Bureau of Justice Statistics released a report in December 2016 which showed that across the country:
3,789,000 people on probation
870,500 people on parole
728,200 people in local jails
1,526,800 people in state and federal prisons.
I don’t have the numbers in front of me, but believe me, I’m going to start looking. All I will say right now is that is a huge amount of money being spent rather needlessly.