If the cost didn't go up, it can't have been a supply shortage. Even at its US peak, there wasn't much of a "fentanyl epidemic" in Mexico either.
The overprescription of opioids in the US (especially in the past) is hardly a secret.
“Even as quality worsens, prices in drug markets are sticky, so the decreasing potency probably meant people were taking less fentanyl.”
“Even as quality worsens, prices in drug markets are sticky, so the decreasing potency probably meant people were taking less fentanyl.”