From my anecdotal experience living in an area filled with fentanyl shooting drug addicts I've noticed they generally are substance abusers with other drugs, such as meth or heavy drinking, ilegally procured prescription pills, cocaine etc., they have groups of fellow substance abusers they meet with daily to combine resources and when the money runs out switch to other drugs that are cheaper to buy like bags of hero…
I moved from California. One thing I noticed that doctors in this area will easily prescribe pills compare to Calfornia. Everyone takes pain killers. Pretty much everyone carries pain killers all the time.